AD—A053 330 51W INDUSTRIES INC KING OF PRUSSIA PA RESEARCH LAB F/S 13/9DEVELOP ENT OF BASIC PROCESSIwS TECI OLOSY FOR €ARINS QUALITY —tIC (U)DEC 77 H N DALAL. 4 W ROSU44EB. L B SIBtEY N00019 76 C—O6S4

UNCLASSIFIED SKF—AL77T05?

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FINAL REPORT

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IJEVEWPNE T OF BASIC PROCESSING TECHNOLOGY .

FOR

BEARING QUALITY ‘SILI(~O$ NITRI DE BALLS

~~~~~

.

DECEMBER 1977

i ~ Contr1butors,:~~~~~~• 11 C..)~~~ •1

. H. . M. DalalL i.&i J.:W. Rosenlieb

L., B.. Sibley

~ U.S. NAVY CONTRACT NO. N00019 76 C 0684

SICF REPORT NO. AL77TOS7StF CODE NO. LC398 . . , ~~~~~~~~~ ~~

‘.

S~F REG. 414 2

* D O C1: Imj j 1~1?~1P-AO f l lBf l~~~~~~~~ :. .SL I ~fl’TED TO: IV APR : 18 Igm I II . U. S. DEPARIIL$’r OF THE NAVY

• . MAVAL~AI R $?IThNS CONMAND . . - ,

~~U ATP 310C tJPI) BWASHINGTON, D C 20360

~REsEARC~~tA.OJtATORY811P INDUSTRIES, INC

- - EN INImIING AND RE$*ARCII CENTER

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KING Oc PNUS~ A PA.

1 : I N A i r p ~~~~~~ON -

J ) E V F LOP~~ NT OF BAS I C PROCESS I N C TE CH NOLO GY

FOR

B E A R I N G QUALITY S I L I C O N N I T R I D E ~ALLS ~ /

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SIJBMI TT EI ) TO:

11. S. DEPARTMENT OF THE NAVYNAVAL AIR SYST EMS COMMAND 0 D CWASHINGTON , D . C . 20360

_______________________________

1 ~~ APR 28 1978 liii

~~~~IBThIBU~TON STATEMENT A U U~~ L6U U i~t~JfoT public r.1.aaij

L D~ati1bution UniimIt.d9

RESEARCH LABORA TORY

5KF I N D U S T R I E S , INC .ENGIN EERING AND RESEARCH CENTER

IcING O~ PRUSSIA , PA

4Lco ~ -

AL77T057

TABLE OF CONTENTS

LI ST OF TABLES ii

LIST OF FI GURES i i i

SUMMA RY 1

CONCLU S IONS 2

PART I - FABRICAT ION OF ROUGH SPHERESAND FINISHED BALLS 3

PART II - PHYSICAL PROPERTIES AND MICRO-STRUCTURA L EVALUATION 7

PART III - EVALUATION OF NON - DESTRUCTIVEFLAW DETECTION TECHNIQUES 11

PART IV - ROLLING FOUR-BALL FATIGUE TESTS 17

LIST OF REFERENCES 22

forWhite Sect~b’~ V~N B’i~t SocUon DI

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RESEARCH LABORATORY SKP IN D U S T RIE S . INC.

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I flat a on (U N V I VaII Zn P on~de r2 f lat a on S I I i con N i t i i de Poi~de r t i s . .’d by Ce r a d v n e3 Sh e e t ro~z l ; i r h i C i ’h e m i c a I Ai ta lys i S O f N C I 32.1 ~l a s t i re n e i i t s on I u d i v i d t n: i 1 Rout~h Sp he re ’~

I FOUl ( ‘C t’a dy n e

5 ~Ie as ii re me n i t S on I i i d i V tu I it (it P re s St.’ ti No ra I i dl,’Sp h c re s I i’oiii N o r t o n

~1i C I’D a rdue s s It.’ as t i r e men t s

Po I ut — t o — Po i n t I)c n s i t v Va r I at i on ‘k’ as n r c d onS I x S i I i con N i t r i de Spec i men s

8 \‘a r i o t l s Tes t C o n d i t i on s A pp l i e d

R o t I i n ~ F o u r - B a ! I Test D a t a t~n 1 . 5 mm Ce ra l b y1 1 — i S i _ N

1 B a i l s

10 R o l I i n ~ Fotil’ —BZI i I l’est D a t a on I . S mm C’I ’ESt _ N 1 R a l I s

I I Ro Ii i ~~ Fotir- R a i l l e s t l : i t i g u t . ’ L i Ic flat a onV .5 mm N o r a l i d e N C! 32 S i _ N 1 B a l l s

12 Est I m a t e d Spa I i i n~ F a t i g i t e 1 10 I i Ic Va I ue’~ b r

No ra l i t h e N C ! 32 and Ct’ radvne il Th ~ i i i conN i t r i d e B a i l s

1 1

R E S E A R C H LABORATORY ~~KF I ND U S T R I E S. I N C .

AL I’O 5

I.. 1 51 ’ OF 1~l CUR E S

11 CIIRFNUMBER 1111.11

V i s u a l i : o n n p a r i s o n of Roug h Si ii con N i t r ideSp hc re s Fro m Th ree S up p lie r s

2 ~I a cr o p l i o t o gr a p Ii S h o w i n g l i g h t and Da rk Grey .- \ r ea son a ~lot t led GTE Sv 1 van ta Cold Pressed a n d S i n t e redS i i i con N i t r i t.le B a i l W h i c h h a s Poor Fat i gue andWe at . I. i Ic

3 l a l v rond ‘I’ r ac e on t l ie Mot t led GTE Sv ivan i a B a l li n F i gu re 2

4 Sc ann i r ig E l e c t ro n M i c rog r a ph s Showing 1)1 ffc ren ccin t h e lie gre e 0 1 Si n t ‘,‘ F i n g B e t w e e n Li ght a n d D a r kRe g i oti s on a Cli Nv 1 van i a B all Stir face

5 S c h e v i ;t t ic D i a g r a m of tilt r a s o n i c M a c h i n i n g ProcessShow i n g El ow o f \h r as i ye Si u r r y Between W o r k p ieeeafl d \ ib r i t i l l ~ 1 Ot) 1

0 t i l t r ason i c Mac l i i n i n g Set — tip f o r B a l l B e a r i n gI nue r R i i i g

tilt r a s on i c Ma ch i n i ng 1oo Is for Pro du c I ng t lieO u t e r R I r ig Ro re ant.! B o t h I n n e r and O u t e r R i n g(~rO oVe s i n B a l l B e a r i n g R i n g s

S A l l — S i 1 i co n N i t r i d e T u r b i n e B e a r i n g M a n u f a c t u r e dby S K F W i t h NC1 32 itot Pressed H a l is andlIlt r a s o n i c a l I M acl i m e d C o l d Pressed and Sinter e dR i n ’~s .

9 Al i-Si ii con Nitride Turb inc Rca r i n g Componen t sM a n u f a c t u r e d by Slfl ’ Show i ng l i l t r a s o nic a I lyM a c h i n e d R i n g Groove s and NC 132 Hot P r e s s e d B a l l s .

10 i r a c t o g r ap h of a F r a . t u r e d GTE Sylvania I)isc(0.43 GP a ) S h o w i n g F r a c t u r e I n i t i a t i o n a t a Pore .Secon d 1hase Inchis ions (A) are Visible a t th eHigher Magn i f ica t ion.

11 Fractograp h of a Fracture d Ceralloy 14TY l)isc(0. S(’ CP a) S h o w i n g F r a c t u r e I n i t i at ion at aSec ond Phase I n c ins io n (B)

12 F r a c t o g r a p h of a F r a c t u r e ’’ NC1 32 Disc ( 0 . 9 9 CPa)I n d i c a t i n g F r a c t u r e r n i t i Z i t i o n at R e s i d u a l S u r f a c eScr at che s .

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1.1 M i c r o s t r u c t u i r e o f Ce r a l l o v 1 4 T h M a t e r i a l F rom a( ‘C r a d v n e ltot P r e s s e d R o u g h Spl it. ’ re . ‘Fli t ’ I n c l u s i o n sin ( d) a r e R I c i t i n I t t r i t im

i S M i c t’os t ruc t u re o I NC 1 52 rade M a t e r i a I t rom(a) N o r t on h o t P r e s s e d R o u g h S p h e r e and(b ) 0 1 di,’ r No r t on B i l l e t M a t e r I a I

1 0 Backs cat t e red F l e c t r on I inage 0 1 N C 1 32 S i I i conN i t r i t.Ie B a l l S u r f a c e S h o w i n g l’ u n g s t en R i cliSc g r e g ;i t i on au d F i n i s Ii P rocess i n g I n d uc ed Sur f aceM i c ro c r a c k s I~h i cli C a u s e d an O r d e r o f Ma gn i t u d eRe duc t i on i n F a t i gut .’ I i I ’el’ r a n s m i s s i on .-\ c ou s t Ic M i c r o g r a p lis o t’ a Sect i o nF r om an N C 1 52 Roi i i ~li Si h ie me

18 ‘l’ r a n s m i s s i o n ~\ c o u i s t i c M i c r o g r a p h o f a S e c t i o nFrom a Ce m a l l o 147 1 Roug h Sp he re

19 T r a n s m i ss i on .-\co ust i c M i c rog r ap h of a Sect I onF roi n a G I L Sv I van i a Rough Sp he t e

20 Sc h e m a t i c Show i n g a St ra i n G a g e d Spe ci men ForC a l i b r at i o n o l N — t’av R e s i t it ial Stress M e a s u r e m e n t‘l’ ec h n I que . D i m e n s i o n s A r e i n mm.

21 Ph o t o g r a p hs o h ’ St i r laces o f (a) GTE S v l v an i a and(b) No r t o n Ba 1 1 P r o d u c e d by K m v p t o n Expos t i reTechn I que . Da mk ( E x p o s e d ) Spots on t h e G’t ’F Sy I van i aH a l 1 a re 1 nd i c a t i ye o I St i r I’ace Po ros it V

22 Schematic D r a w i n g of R o i l i n g F o u r — H a l l T e s t e r2 3 Sch em at Ic I )ra w i n g Show I n g t h e Re I at i ye Pos it i o n s

o I Test and 5uipp o “t P a l is2 4 N o r m a l F a t I gue Spa Ii on an N C 1 32 B all

25 F at i guie Spa l I Caused flue to Repeated Contact w i t hSpa I is on Suppor t H a l is

Mi cr o s p a l Is and W e a r I l ebr i s Found on a FatigueI e s t e d Ce r a i l ov 1471 B a l i

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RESEARCH LABORATORY 5IC F I N D U S T R I E S . I N C .

\ DEVLLOP~.II.NT OF BASIC PROCESSING TECHNOLOGY

FOR BEARIN G QUALiTY SILICON NITRIDE BALLS

S UM M ARY )This is the Final Report on the Development of Basic Pro-

ces sing Technolo gy for Bearing Quality Silicon Nitride Balls.Substantial rolling contact fatigue life data generated onballs has demonstrated the potential of this material forreliable lon g life . To provi de a cost-effective manufacturin gtechnolo gy , fabr ica tion of rough spheres directly from siliconnitride pwoder was undertaken. These were finished into 17.5mmsize balls to generate rolling contact fati gue life data com-parable to that available in the literature. e work wasconducted un der Contract N00019-76-C-0684 .

This report is written in four parts.

Part I discusses the techni que s of formingroug h spheres , and the subsequent machining operations toobta in f in i shed b a l l s .

Part I I p resents the re s ults of I)h Y Si c a l property andmicrostructura l evaluations of the selected materials.

Part III presents the results of the non - destructivetechnique s evaluated for detec ti on of material processin g andfabrica t ion related de fec ts in silicon nitride balls .

Par t IV discusse s the rolling four-ball fati gue lifedata obtained.

-1-RESEARCH LABORATORY SKP I N D U S T R I E S . INC.

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----—-

~~~~~~~~~ ~—-

AL77T 05 7

CONCLUSIONS

1. H ot - p r e s sed s i l i con n i t r i d e can be p ressed into roughbearing shapes suc h as b a l l s having j u s t as good bearingl i f e proper t ies as bea r ing par t s cut from large billets.

2 . Mater ia l qua l i ty i n spec t ion t ec ’ nique s such as u l t rasonics ,acoustic microscopy and Krypton exposure correlate wellwith strength and microhardness properties and have inher -ent capabilities of detecting material de fects in siliconnitride such as inclusions and porosity that are detrimentalto bearing performance .

3. Norton ’s MgO-bonded hot-pressed NORALIDE NC132 gives con-sistantly superior wear and fatigue life perfo rmance inrolling con tac t , when properly f in ished . Ceradyne ’s Y 2O3-

bonded ho t -p res sed CE RALLOY 147 1 wore excessively at hi ghelement test stress conditions , but still had an inherentfatigue spa l l i n g life superior to M-50 bearing steel inthis tes t . GTE Sy lvania ’s pressureless sintered siliconni t r ide wore excess ive ly and spal led at ve ry early l i f e ,due to its relatively high porosity content (2% by volume).

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RESEARCH LABORATORY 5KP I N D U S T R I E S . INC.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Al. 7 7 1 ( 1 ~ —

P A R l ’ I

FARRI CA’F IOM OF ROIJGI I SPHERES AN1 1 F I N I Sh i l i f) BALLS

i . I n t r o d u ct i on

t int i 1 r ecen t lv t h e t a b r i c a t ion o f a fu l l~ de nse s i l i c o nii i t r i d e p a r t f r ee o f bearing Ii Ic d e g r a d i n g de f e c t s con-s is t e d o f p roduc i ng a ful ly dense b i l l e t an LI m a c h i n i n gt lie des i red p a r t Iro uii i t. flut.~ to the e x t me inc ha rdnes s o fs i l i con nitride , this is a tedious and expensive process.Tb is has p r o m p t e d sc ye ral i n v e s t i g a t o r s to e val u a t e me t h odsby w h i c h fu l lv dense be a r i n g q u a l i t y p a r t s can be fab r i -

c a t e d to n e a r ne t s h a p e s . I’wo t ech n i q u e s deve loped ~ofab r i c a t e f u l l y dense P a r t s d i r e c t lv f r o m s i l i c o n n i t r i d epowde r w e r e s e l e c t e d fo r t h i s p r o g r a m . l’he f i r s t is aConvent i ona 1 hot i mess i n g t e c h n i q u e in which s i l i c o n ii i t r i d eI)o~ der mi xet.l w i t Ii s u i t ab Ic t y p e and qu a n t i t v of b i ni de ris P ~~~5 sed in to a sphe i.e shape a t h i gh t e mp e rat ure s ( l o S O ° —V~ 0 °C) in g r a p h i t e d i e s . i ’he second , a p i’ess u r e l e s ssi n t e red p r o d u c t , is a m o re me cent de ye lop une n t (1) * i n whichs i l i con n i t r i d e powder is b l e n d e d w i t h su i t a b l e type andquant ity of binde r and then co ld pr e s s e d t o sh ap e e i t h e rby uniaxial p r e s s u r e u s i n g m e t a l dies or by isostaticp r e s s u r e u s i n g p o l y u r e t h a n e molds . The c o l d pressed pa r t sa re t hen s i n t e red at h i gh tempe r a t u r e w i t h o u t a p p l i c a t i o nof p r e s s u r e as in hot p r e s s i n g . These are re fer re d toas p r e s s u r e l e s s s i n t e r e d p a r t s in c o n t r a s t to r e a c t i o n s in -tere d parts in which the sintering and nitridation ofmetallic sil icon compacts into silicon nitride are performe ds imultaneouslv.

In the p r e s e n t p r o g r a m hot p r e s se d roug h sp here s w e r eo b t a i n e d from N o r t o n and Ce radyne , and t h o s e f a b r i c a t e dby p r e s s u r e le s s s i n t e r i n g w e r e o b t a i n e d from GTE S y l v a n i a .

2 . F a b r i c a t ion of Roug h Sp he res and F i n is h ed B a l l s

The a n a l y s e s of t h e s i l i c o n n i t r i d e powders used b yt h e th ree s e l e c t e d m a t e r i a l s u p p l i e r s are desc r ibed , tothe e x t e n t a v a i l a b l e , in F ab les 1-3. The ph y s i c a l charac-t e r i s t i c s of i n d i v i d u a l roug h sp heres m a n u f a c t u r e d byNorton and Ceradyne are listed in Tables 4 and 5. Fi gure1 provide s a visual comparison of the rough sphere s rece ive dfrom each of the t h r ee sources .

*Numbers in parentheses re fer to the list of re ferencesat t h e end of t h i s r e p o r t .

RESEARCH LABORATORY 5KF I N D U S T R I E S . INC.

A] . ‘l t ) S —

.•\ t o t a l of s i x t e e n expe ri m ental 1 hot p r e s s e d roug hsp here s u~ere p r o v i d e d by N o r t o n Company at no ch a rge fo rt h i s p r o g r a m . l’he compos i t ion o f the material con fo rmsto t h e co~nme r c i al NORAL IDE N i l 32 grade . \s see n in T a b l e Sand Fi gure 1 , these f i r s t attemp t roug h sphere s w e r e o u t —of— i.oun d and had a Ia rge equat cmi a 1 band tdi i ch p roh ib it eduse of a convent ional p r o c e s s i n g cy c l e to f i n i s h t h e m i n t ohea r i n g h a l l s . At t e mpts to remove t h e e q u a t o r i a l b a n dh t umbling was fo un d to be eithe r extremel y s l o w or un re-l i a b l e in a v o i d i n g h a r m f u l surface damage . u l t r a s o n i cmachining was t h e n t v i e d an d th i s p moduced s i gii i Ii cant 1faster m a t e r i a I r e m o v a l r a t e and p r o v i d e d good co n t ro l ont h e s u r f a c e and g e o m e t r i c qua l it v of t h e m a c h i n e d s p h e r e .‘l’he ro ug h s p he me 5 1 ro in Crc up 1 in Ia!) 1 e 5 we me t he me foreroun de d by u l t rasoni cal lv mach in in~t b e t w e e n t w o h e m i s p her-ic a l c a v i t ies . S i n c e t h e p r o c e s s is o f s i g ui i Ii cant v a l u eto mach in i ng ce m zlm i c pa rt s, a b v ie 1 expl ana t ion of the tech —

ni que an t.I its c ap a b i i e s are g iven at the end of thissection. Once the out—of— roundness o f the roug h No r t o nsphe re s i~as reduce d to ‘-a .i mm the~’ could be readil y sub-j e c ted t o the lapp ing procedure previously de ve l o p ed atSKI ’ ( 2 ) to p roduce f i n i s h e d h a l l s h a v i n g an o u t — o f — roundnesso f <0.62 ~mm and a s u r f a c e roughness of < 0 . 0 3 ~m m :\:\ , f reeof h e a r i n g fatigue I I Ce Lle~~rad in~ surface de fects.

‘The Ii ftv roug h sp he yes ~

ro c u r e d fro m Ce rad newere f a b r i c a t e d fro m SS ~/o CP S S s i l i c o n n i t ride I ) O% ~der ,s u p p l i e d by K a w e c k i Be r v l c o , and 15 w/ o \‘~~0 a n d is c l a s-s i f i e d as C e r a l l o v 14 ” I . ‘I’he geome t r i c q u a l i t y of t he sesp he res was good enough to sub i ec t them di r ec t lv to con-vent i onal b a l l p r o c e s s i n g . There appea re d to be some s p o t -t o — s pot va r i at ion in the mach i nab i 1 i t o f t h e m a t e r i a las c o n s i d e r a b l y mo re ext ra care was re qui red d u r i n g thep r o c e s s i n g t h a n in the case of t h e Nor t on sp he res to p ro-duce t h e same de g ree of roundness in the f i n a l l a p p ings t e p . The d i f f e r e n c e in t h e l a p p i n g r e sponse of the ma te r -i a l s is r e l a t e d to the d i f f e rences in the m i c r o s t r u c t u r e sof t hese m a t e r i a l s .

The GTE S y l v a n i a roug h sphere s w e r e p roduced by co ldi s o s t a t i c p r e s s i n g f o l l o w e d by s i n t e r i n g. The g e o m e t r i cq u a l i t y of these roug h sphe res was a l s o ve ry good. A l a rgep ropo r t i on of these h a l l s had a m o t t l e d appea rance consis-t i n g of l i gh t and dark grey a reas ( F i g u r e 2 ’). . D u r i n g t h ecourse of f i n i s h i n g i t was fo un d t h a t the l i ght a rea ma-c h i n e d si g n i f i c a n t l y l a s t e r than the dark a rea pre v e n t i n gthe b a l l s f ro m ro u n d i n g to ‘. 0 . h 2 ,~ m. Tai ron d t r a c e ona lapped h a i l ( F i g u r e 3) shows the s u r f a c e unevenness .

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RESEARCH LABORATORY ~~KF I N D U S T R I E S . INC.

AL~~ 11 )57

The l i g h t e r regions co u ita in la r ger pores than the darkerOne S . l he p0 mc s in the ii gh t e r meg i on w e r e gene ra l 1 yf i l l e d w i t h u n s i n t e r e d Si 3 N . particles ~he reas t h e i~ore si n the da rke r reg ion cont a in re Lit i ye 1 ~ few e r uns in t e redg r’a i n s . The bonding o I t h e S i , ~~ g ma i us i n genie ra I werepoore n. in the li ghter a reas c o m p a r e d to t h e d a r k e r ones .These di f f e rence s are c v i dent in t h e scanning e l e c t r o nm i c r o g r a ph s shown in Fi gu re ~~ .

3. Ultrasonic Ma chinin j~

Hit rason i c mac l i i ii i n g w a s f o u n d to be un i q ue lv app i i —

cab i t . ’ for s hap in g of ha rd Le ran i t .’ s . The ite t h i o t iis analogous to grit blast ing in whi ch a h i ’ a s i ye g r a i n s arep ropel led to the surface to he machined by fluid pressure .The bas i c set - up fo r ul t ras on i c m ac h i n i n g I s show n sc hema —

t ical lv in Li gure 5. The t oo l is v i b r a t e d at a f r e q u e n c yof .0 ,00() s t r o k e s p e r second by an ultrasonic t ransducer.:\ s 1 urrv C o n t a i n i n g 30 - 50 we i ght percent o f a suitableat) ~~ i ye j s a 11 owed to flow between t lie tool and the work -piece. The c l e a rance between the tool auit. l t h e work p iecei s only sli ghtly gm e atem than the si:e of t h e a b r a s i v eb e i n g used . C a v i t a t i o n of t he l i q u i d due to the hi g h fre-q uency v i b r a t i o n of the t o o l generate s a p umping actionw h i c h h e l p s to remo ve used abrasive and hea r debris P ro-duced fro m the w o r k p i e c e .

- T he s h a p e cut in the wo rk p I ece is an e xac t copy ofthe shape of t h e t o o l . Fi gure t shows p h o t o g r a p hs of t h es e t - u p for u l t r a s o n i c a l l y m a c h i n i n g a ball bearing innerr i n g . Pho tograp hs of t o o l i n g to p rod u ce o u t e r ri uigs f ro mc y l i n d e rs and to machine h a i l g rooves in both i nne r andou te r r ings are shown in N gure 7 . Mate v i a l removal ra te ,sur face roug hness a n d d imens io n a l accur a c to w h i c h a par tcan he produced by n i t r a s o n i c m a c h i n i n g depend on theabras i ve g r i t s i : e .

Rough sphere s have bee r produ ced from hot p r e s s e ds i l i c o n nitride cylinders using a slurry containing 50weight percent of 240 grit silicon carbide with a materialremoval rate (MRR) of It1 0() pm (0.040”’) Ier hour. Asmachined sp here s us ing u l t r a s o n i c s had an average surfaceroughness of 0 . 6 pm :\A (24 pin AA ) and an o u t - o f - roun dnessof 40 pm ( 0 . 0 0 1 6 ” ) . Imp rove ment in su r face f i n i s h ando u t - o f - ro un dness is p o s s i b l e b y u s ing a s m a l l e r g r i t si :e ,but w i t h an a c c o m p a n y i n g r e d u c t i o n in m a t e r i a l removal r a t e .

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Groove s have b een m a c h i n e d into silicon nitride ringsu s i n g t w o m a c h i n i n g s t e p s . I n the first step a slurrycon ta i n i ng 50 wei ght percent of 320 grit silicon carb i dewas used to rough machine t h e g roove . In the second stepa slurr y containing 30 weig ht percen t of bOO g r i t s i l i c o ncarb i de was used. The av e rage su r f a c e roughness of thegroove ~as 0.3 rn .\\ (12 in .-\ \ . Th is demonstrates thatby adjusting grit si:e , concentration and type one canuse ultrasonic energ y to either r o u g h m a c h i ne to s h a p e orfinish p01 i sh cc r a n i c s or faces

The tool jog shown in Li gur e — w a s used to ultrason i -

call s ’ machine t h e rings of the all-silicon-nitri de ballh e a r i n g sh ow n in Li gures S and 9. ‘l’his ceramic beamingmanufacturin g p r o c e s s t . I ev e lopm ent demonst r a t e s a g r e a t l yi n c r e a s e d M R R ove r c o n v e n t i o n a l d i a m o n d g r i n d i n g w i t hgreat lv reduced cos t o f t o o l i n g and ab rasives f o r p r o d u c i n gs p e c i a l double curve d bearin g race and roller sur faces.The p rocess c an be re a d i l y s c a l e d - up for p rodu c t ion top roduce dama ge f ree s u r f a c e s foun d to be i mT ipo r tant tor o l l i n g c o n t a c t f a t i g ue p e r f o rmance ( 3 ) .

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to evaluate the p h v s i c a l p rope mt ies and ml crost ruc t ore sof i he h o t ~ m e s s e d i n m a t e r i a l s , sect ions we no made p a r a l Ii’ 1 tothe equat or . The rough sp in’ res p roduce d h~’ I sos t a t i c j ) mes S I rigdo not posst.’ss an equa t or so r am n d umn sect i omis we me t a k e n f r o mhese spin’ res . Ph~’ s i c a l i rope i t i es we me eva I n a t e d us i ng di arnond

p y ram i d ( Vi cke m ‘ s ) in i c r o h a m d n e s s m in e a s t m r c m n e n t s t i m i de r 500 g r a mnload , and strength ineasure m ent ’~ usi ng a b i a x i a l stress t’i xtore .M i c most muc t u i ’;, 1 eva I oat ion was mum ade us i n g opt i ca 1 and s c a n n i n ge I ec t r on mii i cmo s copy

I . Mi c roha rdm ies s Meas u me me mi t s

l) ur i r i g ho t p m es s i ng t h e con tilt I ons used can p ro dt ic ea p r e s s u re g r a d i e n t a c r o s s t h e dia mue t t’ r’ o f ’ t h e main . i)epen—d i ng on the ho t p mess i ng t eIf l I ) e r a t 01, 1’ used , add i t i ye typeand con tem i t and degre e o C p i•c ss u re gr ad i cut the re coo I dbe a dens i tv g r a d i emi t a cross t he ~i I ;imm ie t e r of ’ t he i y e s sedsphe me in a p lane pt.’ rpendi ct mi am to t h e p m ’ess lu g di rect ion .Section s of the Norton and Ce rndvne sp heres we me imiade tode te mmii i ne any dem is i t v g r a d i en t p r es e n t . ‘~es i i It s of in i C ro —

ha rdmies s measu remnen t s nina t.Ie w it hi a di anion d r” rirni d in dent orus i n g a So 0 gram I on ~I a me g I ye mi in ‘l ab i& ’ n . A few r an dourm e a s u r e m e n t s made on a set.’ t i cm i I ’ mc m ii a I ‘I ’F Sv 1 van i a s i Ii conn I t ml Lie sphi c re and a sect ion f’ ro m n a b I h e t of NORM, I DLNC 1 32 grade s i i i con mi it i i de a r e a I so repo r t eLi Ion . corn j i a ri son

Mei s U i’eineii t 5 on t h e sec t i o n f r o m a No r t on sp ir e re s h o w sgood on i fo r t u i t y o C Ii a rdnes s ;mc moss t he Li i am in e t e r . The ha r d —ties s on t h e sp hre me s ec t i o n m s seen to he ii i g he r t han t h a tof am i o l d e r NORA I I DL NCI 32 g r a d e b i l l e t m u a t e H a I . Micro —h a r d n e s s men so re mn en t s a t .’ ros s t he sec t i om i f ’ r om n a Ce r a d v n esp h e r e re vea I s a I a rge h a r d ne s s LI rop a t cc rt a i n r a n d o ml o c a t i o n s . The ha rde r re m ’, i o n s i n t h i s m a t e r i a l ar e c o m p a r a b l ei n h a r d n e s s to t h a t o I t h e N o ii on mum te 1’ I a I . t h e so I te rreg i oas cont a i mi a g l a s s y P h a s e re ~‘ea l e d by p 1 am ie 1)0 1 ai . i :edI I gh t lii i c i ’oSCOj ) \ ’ d i s c r m s s e t l i n t h i s s e c t i o n . lh t . ’s e s o f t e r(we ake r ) meg i on s C mac t ore um i t.ie m Ii i g Im t e m i s i I e 5 t re ss e s

j r i.o t.Iu c e d a t t he ed ge o I t h e con t act m’e g I om i ( 1 ) a n d causew e a r of t l i t . ’ mo I I i m i g t r a c k as LII sc u s s e d I m i P a r t I V . Mi c rch a r d n e s s ~‘a l ime s obta i ned at f o u r I oca t i o m i s on a s e c t i o nfro mn m a GTE Sv I v an i a s p h e r e a me s i gm i i I i cant I y l o w e r t h a nt h e h o t ~ r e sse d m n a t e H a I

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RESEARCH LABORATORY SKF I N D U ST R I E S . INC.

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2 . S t ren gth Measurements

S t reng th va lues for the three m a t e r i a l s were o b t a i n e dby Dr. J . P. \‘enahles of Martin Marietta using a biaxials t r e s s f i x t u r e (5 , 6 ) . T h i s method avo ids f a i l u r e s dueto ed ge f l a w s encountere d in t h r e e - p o i n t and fou r -po in tmeasurement s . D i s c shaped spec imens were f a b r i c a t e d fromthe rough sp h e r e s . The s t r e n g t h value s are compa rableto those measure d by t h r e e - p o i n t bend ing t e s t s on the samem a t e r i a l .

The GTE S y l v a n i a m a t e r i a l , h a v i n g the lowes t hardnessand con ta in ing a si gn i f i c a n t amount of po r o s i t y , has thelowest s t r eng th of 0 . 4 3 GPa (62 b s i ) . The Cerad yne m a t e r i a lhas the next hi ghest strength ’i of 0 . 5 6 GPa ( 8 2 k s i ) .Norton material showed t h e hi ghest strength of 0.99 CPa(144 k s i ) .

Fractographs made w i t h a SE M are shown in Figures10-12. Porosity is clearly responsible for fracture initia-tion in the GTE Sylvania sample. A hi gh magn i fication viewof the pore surface does not reveal unsintere d siliconnitride grains , probably since they may have been dislod gedin the fracture process. In the Ceradyne material a clusterof second phase particles (free Si) was responsible forfracture initiation. A h i gh magnification view of the frac-ture surface show s presence of a large volumiie fractionof the second phase particles. Fracture initiation inthe Norton material appears to have occurred at surfacescratches. The degree of material cleanliness and absenceof porosity explain the hi gh strength value obtained forthe Norton ’s NORALIDE NC132 grade silicon nitride .

3. Microstructural Examinations

hlicrostructur es of the three materials were studiedwith the help of optical and scanning electron microscopes.Bo th unpo l a r i zed an d plane polarized lig ht were used duringopt ica l mic roscopy . Since the o p t i c a l p r o p e r t i e s of thevarious p hases present in t h e thre e s i l i c o n n i t r i d e compo-s i t i o n s are not known , it w a s not pos s ib l e to de te rmine t h etype of phase seen on the micrograp h. The r e s u l t s are re-ported to document the p r e l i m i n a r y o b s e r v a t i o n s on theop t ica l c h a r a c t e r i s t i c s of the va r ious p hases obse rved .

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compos it i ours ar e sh own i i i Li gu m e s 1 3 — I f~ . The G’IT, S 1 van i amate r i a I con t a t ire Li air es t i mat C’ tI S yb 3 v/ o 1 a mge + 2 ybye F\’ Ii flC’ ) secon LI phase iii c I us i om i s 0 F l go me I 3a) . ‘Fire l a r g ei mi c 1 us iomi s rema inc LI dark whe n v I owed in ~ h ;mne po I a r i z e Li

li ght (Fi g u r e 1 3h ) . Po i’osi tv leve l is est i mat L’LI t o be2 yb (Li gore I 3c ) . R a c k s ca t t e med e l e c t ron i m a g e ( 1 : 1 gore1 3d) at a hr i t.~h nuagn i t

’ I cat i oni reveals a nic e’ LII e — l i k e s t ruct ore

Tires e rep rese ni t ct— S i ~N , needles t hi n t fo mm w i th in theam mo rphous S i N’ pa r t I c I CS ~hu r i r i g i n it I a I C r’\’ s t a 11 i at ion ( ‘1

‘l’he Ce radv ire mate mi a I a I so cont a lire ~I 1 a rge and s ma ) Isecond pha se i nrc I us n 011 5 ( L i go re I 4a ) . ‘l ’h ie I a rge ones turneddark in p I ane po I a r . i :L’ LI Ii girt (1 :1 gui’e 1 l b ) . ‘ftc p l a n epo Ia r’i :ed I i girt mi c rogmap hi a I so reveals a pat d r 01 g I a s s vma te r i at . Some a me as i n t i r e mate ri a I com r t a i ire LI ye rv 1 a rgepatc lr es o I g I a~ cv mate r i a I (i~ i gir me I ‘I L’ ‘1 . Ch enr i ca 1 a n a l y ~ j ~c o n d u c t eLI us i rig a wave 1 L’m i gt ii spec t’ i’omne t e r i i i Li i ca t I’ LI thatt i r e Ia rge i nrc h i s I om is a me r i cii i n s i I I con a i r Li tire re fo reI i ke ’ ly t o bL ’ t n’e e 5 i i i con . I ’i re g i n s sv pha se i 5 r i chic ri n vt’ t r. I u rn t h a n t h e un:u t ml ,~ and t h er e Co me I i ke I v to beV t t m l urn s i I I co m i O \ V i i i t i i L I L ’ ( ‘V . 5 i Ii •~N . ) r e p o r t ed t o he i’~ resent In t hr i mat e n .i a I (I) . I t t mi ~n m r i d r I mr c I us i o n s we rea I so fO umi Ll (1:1 gore 1 .1 L I ) . ‘l ire com npo tin LI t o i’mii o f ’ t ire 1 at t e ry~ t ri win H cli i n c 1 us i o n was not e s t ab Ii shed.

l i re NORA1.I DL N ’ i 3. t’, r;ide s i l l co ir nr I t m m tI L’ us ed i n t i r eNo mt on sp ire res I 5 me I a t I ye I ye my L ’ I c an cempa me ti to thep r e v i o u s two m a t e r I a Is . Omr I ~

‘ a t’ew ye my stu n I I S L ’comrd pi ras t.’i irc l us lori s cons i st iii 0 1 1 n’e ‘— i 1 I com r ~i ’~ c ec I .i t eLi w i t ir nw’ t a Il i c ( b r i g h t ) p a r t I L ’ I L ’s w e r L ’ t’o m n n r d ( i n ~~l l r L ’ I S ~~). l’Iris i si n agreement w i t ii No i’t our ’ s owir I i mrd i mr , :s ( S ) . P I ami e p o l a -

ri zed i i girt v I ew o t t he ante a i o n ( 1 m gi m it. ’ I Sb ) s i r L)W s at’i ire di spe rs i omr 0 I’ g I ,m ‘~ ‘~ ‘ p it ,1SL ’ . h e m ’ L ’ o n u i ) a m i ‘— eu a in i c meg m a p i r of air o i L i e r ’ s~ m n ’t p l e 0 t \ t i R , ’\i I ir E NC I 32 i ’at . i e ~ i I i conii I t r I tie i s g I ven i I ‘ I grime I f~ ~_ ) . h e m ii c I i i m our L ’O n i t L ’ m i t otir e oh tiC i~ m a t e 1.1 .i I i ~ I a mgi ’ F i i i qtmar r t i t ~ , i m r Li I :e e’omp a r e ~ito t h e p res ’ir t hat L’ Ii , I I ~~~ei ’S i n g a L O ! i S m d& ’ n ’ah I e i nip n o ~‘ e m m m e m ri n p r oL ’es s i n t~ t cdi i i i qLI t ’ . S L ’ a n n r i mi ~ e I e L ’ t rom i un L ’ n’os cops’o f t h e s t VII I’ t in me di d nrot me Vi ’ a I any t ir i rig me r e t i r a n t i l L ’

ta mi I i a r L i i st ri ho n on e C 1% — i i cli i ir c I us i o n s iii S I ~N n i . i t r i

f o u n d i n NC 1 3L’ mat e mm a I ~

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RESEARCH LABORATORY SKF I N D U S T R I E S . I N C .

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:\ c u r s o r y e x a m i n a t ion o f ’ four lion— dest ruc t i ye t ech n i qL mesto de tec t mat e r i a l and / o r fat ) ri cat i on i.e l a t e d f l a w s w a s c o n d u c t e d .‘I ’hi esc are :

1. t J l t m a s o n i c I n s p e c t i o n2. Acoos t i c Mi croscopY3 . Krypton Fxposume ‘l’ecirn i L~ue ( KN ’ i ’ l4 . Surface Re s i d u a l St res s Me a su r emne ’nt

us i n rg X—ray Di f f m a c t l o i n

1. ( l I t ra son I c h1~~ e c t i o n

‘l’his w o r k was p e r f o r i m n e d at ‘U Ric , inc. , using t h e i m i s t r u —m e n t a t ion and t e c h n i q ues d e v e l o p e d ui m LI e r N A ~’, \ l R cont r a c t s(9 , 10) . Exam in at i our s we me coi n ii oct ed us in g 15 MhIz lon i g i t o —di na 1 and s h e a r w a v e s . Long i t rid i o n 1 waves we me USCL I toe x a m i n e dens i tv va ri at ion from po mi t — t o — 1)0 i mi t . Shear wavesdue to their shorter wa velen gtir (hence be tt er r e s o l L i t iL ) i i )were used fo r d e t e c t i o m r o f ’ po ros I t \ ’ and i n c I n s lon is.

S i x s e c t j o i n s ir a v in g a t i n i c k m r es s o 1’ 2 + (1 . (15 mum w e r ep r o v i d e d for tin i s st ud~’ . ‘i’ ines e a re : - -

a) NORM,1 DL Nt ’ l 32 h i 1 l e t s e c t I onb) NOR,\I,l DL NC 32 b I l l e t s L c t i Oh coOt a i ii jug mi cr0—

h a r d n e s s in t ie n t a t I ens nn a de at I , (1 • 5 , (1 . 3 ami d(1 . 2 kg I on ds

c) N O RAL I D E NC 1 32 ~0W L I c r ~ rocL’sseLi h a l 1 s ec t ionmade p(’ rpe mid I c m l a r to the eq oat o i.

d) Ce ra l b y 14 “‘r ’ p o w d e r n r o c e s s e ’d ball sect ion madep e r p e n d i c u l a r to t i r e e q u a t o r .

e) Cera l 10) ’ l ’I \’ p o w d e r pr o ce s s ed b a l l s e c t io n maL leparallel to t he e q u a t o r .

f) GTE Sv 1 va in i n powd e r p r o c e s s e d h a l I s ec t ion

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RESEARCH LABORATORY 5KF IN D U S T RI ES. I N C .

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Accordin g to McLean , et al (11) the density variationwith velocity for silicon n’iitride is 0.2 g/ cc/knn / s .The si gnal was allowed to reflect four times befo re recor-ding its time of flig ht through the material at each pointto imp rove t h e resol Ut i o n in veloc ity mut easuren n en t s andthereby the r e s o l u t i o n in d e n s i t y v a r i a t i o n . The a v a i l a b l ea c c u r a c y in the t i m e o f f l i gh t meas ur eme n t i s + 8 nanoseconds( 8 x I O 9 secs .) . In t h e p r e s e n t case t h i s c o r r e s p o n d s to ar e s o l u t i o n in d e n s i t y o f + 0 . 0 0 1 g/ c c .

The velocit y r e a d i n g s t a k e n and e q u i v a l e n t d e n s i t yvalues at five points on eacir of tire six specimens arelisted in Table 7. Statistica l evaluation of tin e uneasure-nrcn t s shows t h a t t i r e den s i ty va n a t i o n s n u m e a s o m e d on t h etwo Ceradync samples are si gui f i c a n t w h e r e a s those m e a s u r e don the o t h e r f o u r sann p ~ es are w i t h i n e xu e r i n r e n t a l e r r o r . Tireg r e a t e r dens i t ’ v a r i a t i o n foun d in the Ceradyne s a m p l e sis in con fo rmance w i t h t h e g r e a t e r v a r i a t i o n r in i t n i c r o h r a rd-ness va lues o b t a i n e d ou r the same material.

A t t e m p t s to de t ec t i n t e r n a l f l a w s in the di f f e rentmat e r i a l s or m n ic ro h a rd nc ss i n d e n t a t i o n s on t h e NO R A L I D ENC 132 b i l l e t s p e c i n n e n were u n s u c c e s s f u l . T h i s i s c o n s i d e re dto he l a r g e l y due to i n a p p r o p r i a t e n e s s of t h e a v a i l a b l e

F t r ansduce r for t he t h i n s ample s used. A s h o r t w a t e r p a t hof 2 cms . w a s used to n n i n i m i z e s i g n a l a t t e n u a t i o n ari d the re-b y l oss i n sen s i t i v i ty . ‘I’ he a v a i l aLi 1 e t r a n sd u c e r , h a v i n ga focal l e n g t h of b 3. S m n niu n ( 2 . 5 i n n . ) i n w a t e r , w a s des i g n edto be used w i t h 8 . 2 5 mm ( 0 . 2 5 in) t h i c k s pec in r en s . Tir euse o f 2 mm t h i c k spc i r n e m r s in t in e p resen i t s t u d y d i d n otpe rmi t the a c o u s t i c beam to focus w ith in t h e 5P 0C inne n andthe re fo re the e x a m i n a t i o n w as con duc teL l at l e ss t h a n opt i m um i nc o n d i t i o n s . Th e s ma l l s p e c i u m ne n t h i c k n ess w a s esse n t i a lto be a b l e to e x a m i n e t h e n r a te r i a l o f t i r e roug h sphe re sas c lose to the edges as p o s s i b l e w i t h o u t i n t e r f e r e n c efrom t h e c u r v a t u r e of t ire s p h e r e .

Sur f ace m i c r o h a r d n e s s i n d e n t a t i o n s are not d e t e c t ab l eby C-scan t e c h n i q u e us in g e i t h e r l o n g i t u d i n a l or s h e a r w a v emodes due to t h e p re sence of a 4() urn dead h a n d p re sen r t near ’the top and b o t t o m s p e c i m e n s u r f a c e s . T h i s i s caused dueto the i n t e r f e rence b e t w e e n i n c i d e n t and re f l e c t e d beams .The m a x i m u m dep th of t h e r n i c r o h a r d n e s s i n d e n t a t i o n in t r o -duced at 1 kg is 4 u rn . L o s s - o f - b a c k - r e f l e c t i o n i n t e n s i t ymeasure ments w e r e made u s i n g long i t u d i r r a l wave s and p l a c i n gthe i n d e n t e d s u r f a c e f a c i n g down. The m i c r o h a r d n e s s inden-t a t i o n s were not d e t e c t a b l e . I t is c e r t a i n t h a t use ofa p roper t r a n s d u c e r can i m p ro ve t ir e s e n s i t i v i t y of th r e s h e a r

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- i i -RESEARCH LABORATORY SKP I N D U S T RI ES. IN C .

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wave mode consid erably . Use of tire surface wave technique ,pre s en t ly be ing d e v e l o p e d at TR W , I n c . unde r a N A V A I R con-tract , woul d enable detection of surface flaws such as tir em i cr o h a r d n e s s i n d e n t a t i o n s . The inden t at ions are much lar-ger than the l a r g e s t t o l e r a b l e s u r f a c e f l a w or one t h a twoul d be g e n e r a t e d by s l i g h t l y abusive f a b r i c a t i o n methods .The u l t i m a t e t e s t of a s u r f a c e f l a w d e t e c t i o n t e c h n i q u ewoul d l i e in i t s a b i l i t y t o de tec t s i gn i f i c a n t l y s m a l l e rs u r f a c e f l a w s of the t y p e shown in Fi gure lu produced ona b a l l s u r f a c e by an imp rope r l a p p i n g p r o c e d u r e . Re mo valof t h i s dama ge d s u r f a c e i m m a t e r i a l p roduced a m i n i m u m improve-ment in tin e L ~o l i f e o f the b a l l s f rom 7.55 x 10 6 revs .to 36. 7 x 10 6 revs. (2).

2. Acoustic Microscopy

This is a d e s i r a b l e n u n o d i f i c a t i o n of the C -s can u l t r a -son ic i n s p e c t i o n t e c h n i que . ‘fir e Li e sira b i lity is in thefact that an image similar to that of an optical microscopei s p ro duced , simp lif y i n g interpretation of the info rmnation.The commercia l model ‘SONO MI CRO S COPE 100’ was used for thisstudy . I t uses 100 ~llIz s h e a r waves and i s c a p a b l e of p ro-ducing a di rect image of t ire t r a n s m i t t e d a c o u s t i c s i g n a lshowing the a c o u s t i c a l l y d i f f e remi t f ea tu r e s encounte re din the volume t h r o u g h w h i cii t h e b e a m was transmitted. Ita l so produces a c o u s t i c i n t e r f e rence image s s i m i l a r to t h et y p e of image p r o d uc e d in opt i cal j u t e r f e rence m i c r o s c o p y .A n a l y s i s of the f r i n g e p o s i t i o n s p r o v i d e s q u a n t i t a t i v e in f o r-n i n a t ion on a mi c r o s c o p i c sca le r e g a r d i u r g t h e e l a s t i c proper-t i e s of the r eg ion s w i t h i n air i n s o n i f i e d vo lume . The con-ve rs ion of the a c o u s t i c s i gna l i n t o a rea l t i m e image ona t e l e v i s i o n m o n i t o r i s done by m n n eans of a hi gh r e s o l u t i o nl a s e r m i c r o p h o n e (12 , 13) .

The t echn i que depends fo r i t s d e t e c t i o n our the degreeof a c o u s t i c m i s m a t c h b e t w e e n t in e mat r i x and t i re f l a w .A c o u s t i c impedance ( ) is de l i ned as t i re p r oduc t of d e n s i t y(p) and a c o u s t i c v e l o c i t y in th e m a t e r i a l (v ) wh i ch in t u r nis a function of elastic modulus and density.

= cv

The degree of acoustic mi smatch is defined as

-12

RESEARCH LABORATORY SKF IN D U ST R I ES. INC.

r ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

_ _ _ _

.\ L ’~ I ’ O S

win e i’e = aco m ist i c i mumped air cc o 1’ 1,1 zuw

un= acous t i c I m p e d a n c e of ’ mat r i x

S i n c e t i n e s t r e s s r a i s i n g ah ) i I it )’ of a f l a w a n d a c o u s t i cm i s m a t c i n a r e b o t h i n sonune w a y f u n c t i o n s of t i r e degree ofe la t i c mi sun a t ch be t m~cen the 1

,1 ant ’ and tire mat m ix , i t i s

e v i d e u r t thna t ti n s t e c h n i qu e w o u l d d e t e c t t i re most s t r e i n g t hdegradi rig flaws ii rs t . iii i s i s a t’L’ r des I r’ab IL ’ cap ab j i l t ”of tir e tecin nn i que .

l i r e res 01 m t j our o f t he acous t I c min i c me scope i s app ro x I —

m a t e l v one w a v e i e n g t i n of sourn d in t ine matei’ i at bein g lu nves -

t i gated or app no x I n mm a t ci v 50 ~jm in h ot p me s seLl s I I I corr ur I —

t ride . ‘I’lre seir s it i vi tv i s e st nu a t e d to he one— fi f’tir t h i ss i ze . Acous t i c umn i c no grap hs o f tine tin nec s I I i con in i t ri dem aterials used in this p r o g r a m a re s i r o w n u n F i gui ~es 1 ~~~

- l9 qas obtai rred at Sonoscan , lu n c.

An i nra go o I an acous t i cal 1 y homuro geineous nra ten ’ in 1 wou I dbe mon iot om nous and t ine i n t e r l’c r e u n c e i ma ge wou 1 d show st r a i g i r ti u ’r te rf e rerrce l i n e s . ‘b in s is seeu i to be t rue o f ’ t h e NOR:\I,II)EN ( ’ l 32 ma tL ’ ri a I I, Ii gin re 1 “) . ‘Fire acous t i c m m c rograpir oCe ra l b y 14 ~Y (F i gure 18) sinows reg ions that are bothi i gin ter’ and Lia rke r t h a n t h e mat vi x . The I i girt er f e a t u r e sare iunc in s ions rci th a lower acous t i c at tennuat i on than tirem a t r i x w h e r eas tire darker reg ions are regions w ith higherat ten oat ion aur (I a re 1 i he lv to be f i inc pores i in t h e m a t e r i a l‘Fire sir I f t o f t h e i rite r Ic n’ cnce f r i n ig es to t h e l e f t inn t heIi gir t a p p e a r i n g i inc I us i our s i s i m r d i cat i ye o f lower a coust I cv e l o c i t y i n i t compare d to t i r e u n a t n i x . A c o u s t i c i n i c r o g ma p ho f t i re GTE Sy 1 ~‘ain I a mu m a t e ri a I ( Li gure 19) sh ows l a r g e r 1 i girtand d a r k re g i our s i rid cat i ye o I ~ rese m n cc o I’ I a n ge l’ s i ze i n n -

c I us io n s a n d po re s i n t h e m a t e n~ in 1 . ‘l’he pnc seirc e o I po~’~ -

si tv in t h e GTE Sv 1 vaun i n mu iat e ri a 1 h a s bee n e s t ab 1 i s i red by

ot ire r m e t h o d s o f e x a m i u i a t i on . Fr a c t o g r ap h s oin t i ne Ce ra 110)’1 4 \‘ m a t e n i a 1 s in ews p r e ence o I f ace t ed gm i n s win i cm coo l Li0cc ur c i t Ir e r Line to a t i’air s g rairul an’ mode o I f r a c t ur e o rp resence of ponos itv . Occurrence of ’ LIa rk reg ions on t i nea c o u s t i c microg ma ph i r r L l i c a t e ,~ t h a t some o f ’ t ine unr bond edgrain surfaces ~‘ i s i b l e our the f r a c t o g r a p ir n rust be d u e tot h e p re sence of po r o s i t Y .

Reg ions of low a c o u s t i c v e l o c i t y in Ce ra l loy 1471foun d in 4 5 ~l l I z i n s p e c t i o n we re a l s o d e t e c t e d d u r i n ga c o u s t i c mic roscopy i nn s p c c t i o n .

*

- 1 3RESEARCH LABORATORY SKF I N D U S T R I E S . I N C .

,\I ~77’I ’0 5T’

3. K n v p t o n E x p o s u r e T e c h n i que (~~F’I ’)

T h i s i s a r e l a t i v e l y u n ew n o n - destructive test techniquef o r de t ec t ion of s u r f a c e f l a w s . In p r i n c i p l e i t is s im i l a rto t ine c o n v e n t i o n a l dye peu r e t r a n t me t inod o f d e t e c t i n n g s u n -face fl aws w h e r e the conven t i o n n a l dy e i s r e p l a c e d by radio-a c t i v e Krypton (Kr 85 ) . ‘I’he latter is a fissio rn by-productof 112 ~ produced in n u c l e a r f i s s ion r e a c t o r s cour t r o l l e d byti ne I i . S . G overnn rn e in t

Par t s to he e x a n n i nned a re i ’l a c e d in a v a c u u m c h a m b e rw h i c h is e v a c u a t e d to a p r e s s u r e o f 10 urn of 11 g. TIre cham-ber i s t h e n h a c k f i l l e d w i t h Ku’ gas c o n t a i n i n g a b o u t 5~r a d i o a c t i v e K r , t h e r e s t b e i n r g s t a b l e K r . ‘l’he P a r t s a reai lowed to s oak in t i r e gas fo r’ about o n e inoui ’ . The soakedp a r t s are removed f r o m t i r e c h a m b e r and c o a t e d w i t i r a p h o t o -graphic emulsion . ‘I’he enrulsion is exposed fo r a p e r i o d of24 hour s ain Li t he i r de v e l o p e L l f o r d e t e c t ion o f s u r f a c e flawswhe re Kr 8 5 embedde d d u r i n g t ine s o a k i n g o p e r a t i o n . Severa lp r e c a u t i o n s nnu s t he ob ser v e d in u s i n g KET fo r d e t e c t i o n n ofs u r f a c e f l a w s . Sun faces o f t ine p a r t s s in o u l d be t lnoroug inl yc l e a n e d as d i r t ca in a c t as a t r a p to K r ° 5 .

The c h a r a c t e r i s t i c s of t i re p h o t o g r a p h i c e m u l s i o n usedare s i m i l a r to d e n t a l X - r a y f i l u n . E u n e r g y of t ine s - r a d i a t io nem i t t e d by K r 85 caun he c o m p l e t e l y a b s o r b e d by an emul s ionnt h i c k n e s s of 80 urn w h i c h i s t h e r e fo re tir e o p t i u n u n n t h n i c k n e s s .E m u l s i o n t i n i c kn e s s e s muc h s m a l l e r t h a n 80 urn w i l l lose asi g n i f i c a n t a iunou nr t o f e n i e n g y t h r ’oug h t r a n s n n i s s i o n . T i n i c k e rc o a t i n g s w i l l nra ke d e t e c t i o n o f exposed a r ea s mo re d i f f i c u l tdue to the prese ince of an ovem la er o f u n e x p o s e d e m u l s i o n .In p r a c t i c e , a t t e m p t s are made to c o m i t r o l t i r e t i r i c k n n e s s o fthe p h o t o g r a p in ic e i u m u l s i o n b e t w e e n r 51) ani d 80 u rn. In p a r t sc o n t a i n i n g f i l l e t s and u n d e r - c u t s t h i s can be ac i r i eve d byr e s o r t i n g to a m i s t sp r ay t e c i n n r i q u e of a p p l y inn g the e m u l s i o ni n s t e a d of d i p p i n g t ine p ar t s in t ine e m u l s i o n .

The s e n s i t i v i t y of KE T i s l i m i t e d o n l y by t in e g r a i ns i z e of the e m u l s i o n f i l m , so t h a t i t can he expec ted t ina ta max imum s e n s i t i v i ty of about 4 urn w i l l be o b t a i n e d . Foran i n i t i a l e v a i u a t i o n n o f t h i s t e c h n i q u e one GTE S y l v a n i aba l l and one N o r t o n f i n i shred b a i l were e x a n n i n e d at QUA L - K ,I n c . The GTE S y l v a n i a b a l l , h a v i n g a l i g irt co lo r , was p ro-cessed as i s . The d a r k e r co lo re d N o r t o n b a l l was coated w i t i nT i 0 2 to imp rove t i re v i s i b i l i t y of t h e exposed a r e a s . Thiswas n e c e s s a ry s i n c e i t was fo uur d d i f f i c u l t to peel t ine ernul-siour o f f t h e h a i l s u r f a c e fo r e x a m i n a t i o n w i t i r o u t d i s t u r b i n gor b r e a k i n g i t . Tin e da rk c o l o r of the h a i l nrad e i t d i f f i -cu l t to see any da rk exposed a r e a s onn t i re o v e r l a y iun g f i l m .

— 1 4 —

RESEARCH LABORATORY ~~KF I N D U S T R I E S . I N C .

U ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ U

:\1, ” 105

Itre Wi i’K ~ pot ~— Oil tine t l’F ~v 1 ~‘an n I a ha 1 1 s s h o w n I n r I i g o r e~ 1 r in d i c a t e t in e r me s e u r cL’ 0 I s u n ’ lace po t ’os it y h n i o i ~nr to e \ I 5i n n t i n is m a te ri al I Femu r o t h m e 1’ e \ a m i n a t i o u r s . Ku I m d I ca t i o n s a n’evi s ib Ic urn

, t i r e No m y cmi ha 11 . l im e t echnn i q ire Ira s a LIC ft nr it eadvan tage n nr thr a t i t c a in e ~a ml in c t ln~’ emit i n’e sum’ IaL ’e s 1 n i u rlt an n e o u s lv comp a red to Ot i r e F t cc hu n i L ( L I L ’ 5 i~ ir e re p0 1 ni t — t O— ~)Oi ni ti n n s p e c t i on is reL (mi I red. i or ’ t i r e t e c i r n r i qu e ‘ success a sa rou t I ire I i n s p e c t I our t o o l I’o r h e n i i m r~ com imp o n ic u r t s , I t i sneces sar ~ to Lie ye I op b e t I C 1’ ne t h r o d s t o m ’ ap p I I c a t i our a n di’e mmio ~‘a 1 o I’ p i m o t og m p h i c enm u l 5 t o n i t O I’ L ’ X i i i i u r n I 1 0i~ . \Ll L ’L h Li ~L t ek n r o w l e d ge of ’ the co n’re l at t on i he tw cc mr the presL ’nrce of au rim rd i cat loin and it s s I :e r~ it ii t i l L ’ t v P~’ air LI S I :t ,’ 0 1 t in L ’ sum -

fac e t’i am~ app eai’s t 0 h~’ I ac K i n n g a t t h e ~ nc s c n r t t i m ime

4 . Sum’Ia ce Res I L I u a i St m e s s ~I e a s i i m ’ e m imenr t s b y \ — na y I i i I’ f i ’ ac t b u n

l i r e mu m m L) r l t v 0 f’ t ire i’o I I in n g cent act fat i cue ía I in i’e s e m uco u u n t c red I m u s i b i co in nr i t F l iL’ a n ’ e s u r f a c e u n t i n ted (1415 , l~ , 1 T ’ ) . ‘I ’ire sc smii ’ f n L ’e i i i i t i at ed f a i l m i r e s c a r r h e s i g—

ur i t’i c am r t I V a I ’ i c c t e d by t he type am i d umma ,gn r i t mmdc o I’ si n rfacci’es idua l st r e s s e s produc ed d u r i n g I’a b i ’ i c a t lo in o f ’ a c o u m r p o n e m n tE f fe L’t o I’ ~‘ roces s I i r g pa m an ure t e u~s o n t i m e st m ’enr gth and t ’a t I ~ m mei i Ie o f ’ mun e t ;i Is inn s b e en n l on u g es t ah I I sh e~i I. I S , 1 9 ) . A d ap t :t t l o i no 1 tin e incas Li re mu iem n t t ecu in i q ti e ( 2 ( f ) t O S 1 1 i coin in i t m i Lie woo 1 dp no m’ I ~le a mea n s o I’ de v i s b u r g f ’;ih F I cat I o ir r m ’ o ce s S L ’5 to gL’ire —

r a t e s u r f a c e c o m p r e s s i v e s t r e s s e s .

Cal i in r a t i o n o I t i r e t e c i n m n i L(ue us i mr g t i r e es t ab 1 i s hedp roce do me ( 2 0 ) ica s con duc t CLI w it hr t h e hiL ’ I i~ 0 I’ a beam i m ~ mu —

m m deLi by No u ’t on a n n d a I’o n m F — po I mi t h e n r LI iii g at t a c i r n n e m r t f o rt i r e K— m v mach i I i r e . l i r e as — r ecL’ i ved he a imus r~e re I’ iii i s hi edto 10 x 1 . S x 0 . 2 cm n un LI s t ma u n gaged as s m own i n 1: 1 go m e2 0 . Tire 72 0 ~ —S I 3 N~ pea k 1 ocat L’Ll a t 2~ ai ng l e o I 14 7 .Lieg rec s w i t in coppe u’ mad i at I on ( I ) nu L l a i~ — rot at i on o f’4 50 we me Lis e Li . l i r e s t mess Inc tot ’ nu de t. t h e s e c o m n d i t I onrsI s ca I c m i i a t ed to be I 98 Ks I / deg ree . t h e un ea so red va 1 ueo f t ire mat i o ( E l I + u) = 2 5 0 . 2 5 GPa 1 3 . (~ x 10 ps i ) wine reE I s t h e L ’ I as t i c nu m odu h i s o t’ die smu m i n ce m a t e r i a I air d cI t s Pu i s sour ‘ s r a t io . u s i n g a ~‘a I ire o I o = (1 • 2 5 tIre t ’a 1 inco t’ F i s c a b c u l at ed t o be 32~b . 0 7 GPa (4 x 1(1 ~ ~~ I ) . Tin i sI s iii good a greemu m en i t w it ii t h e 1 i t e r a t m i m e ~‘a I inc 0 f ’3 b 0 . 2 ~ ( ; Pa ( 4 5 ~ io ~ I n s i ) .

4

*

- is-

RESEARCH LABORATORY 5KF I N D U S T R I E S. I N C .

-,‘~~~~~~~~~~

-- _____

AL 77 TO 57P A RT I V

R O L L I N G FOUR-BALL FATIGUE TESTS

The expe r i m e n t a l e v a l u a t i o n o t h e f a t i g u e l i f e of t inet h r e e gro ups of S i 3 N ~ b a l l s was p e r f o rmed on r o l l i n g f o u r - h a l lt e s t e r s . The tes t s e r i e s was desi gne d to d e t e r m i n e t ine r e l a t i v ed i f f e rences in the fa t i gue l i f e of the th ree group s and p rov idea compar i son of the l i ve s w i t h t ir a t I r e v i o u s ly o b t a i n e d fo r CVMN-SO steel balls and NC 1 32 g rad e s i l i c on ni t r i d e h a l l s manufac -tured from a hot pressed billet (2).

R o l l i n g Four-Ball Tester E, Test Procedure

A s chema t ic of t he ro l l i n g four-ball tester is presented inFi gure 22. In the four-ball tester , the test specimen , i.e. thesp i n d l e b a l l , is h eld in a ve rtical arbor against thre e supportballs which orbit the spindle ball in a stationary cup race. Thespindle ball is fi xed in position with respect to tin e rotatingarbor by a spring loader/plun ge r p res sed against a flat surfacegro un d on the top of the spindle ball and tin e friction betwe cun thecon e machined in the end of t in e arb o r and t ine h a i l s p h e r i c a l sur-face . Two f la ts ar e mach in e d on each sp ind l e h a il di a met r ica l lyoppos ite each other; thus , each hail is tested twice , i.e. ea ch iend is considered as one test specimen.

The support halls are positioned in tin e cup race 1200 apar tand held in this relative p osition by a brass cage or separator.The positioning of tin e cup concentric with the spiundl e axis in-sure s equal loading of tine support balls and identical Iiert:ians t ress at the thn ree con t ac t p o i n t s be tween the s p i n d l e ( t e s t )ball and the support balls. The contact angle of the assemblyis controlled by the race desi gn in the cup and tir e support andtes t bal l s izes , see Fi gure 23. The load , win c h determines theHertz stress at the contact points between tir e halls , is appliedthrough the spindle by a dead weig in t leve r sy stem. The sp indlei s driven by a constant speed AC motor tin roug h a pulley and beltdri ve sys tem. The spindle speed can be varied by changing thera tio of the drive to driven pulley diameters .

L u b r i c a t i o n is p rov ided by a o n c e - t h r o u g in , d r i p - f e e d s y s t e m .The oil is fed into the bottom of the cup and flows out of tiretop thus main t a i n i n g a copious q uan t i ty o f oi l in t h e cup forlubrica tion of the contacts. A vibraswitcin mo unted on the cupsuppor t t able au toma t i ca l ly turns th e drive mo tor o f f and stop sthe testing at the initiation of a spalling fa i l ure .

- i t,-

RESEARCH LABORATORY ~~KF I N D U ST R I E S . I N C .

Al ~~T 05

Pr ior to t i r e i i r i t m t j o u r ol’ eacir test , t h e c o n n c e m n t n i c i t vof tin e cup race w i t hr r e s p e c t t o the sp I i r d i e ax i S 1% as det e mii i nredw itir t h e o p e r a t i n g l o a d appi ted and an~’ n eces sar\’ adi ustn ircul t 5made . Fin e cup race m~ as v i s in n 11 v e x a m I n i ed t o r L i au m mage , ami d i Idamage was p r e s e n r t t i r e c u p w a s n’ep l a c e d . Tir e sp i n r d l e ball ,s u p p o r t b a l l s am i d cup we re c l e a n e d be fo me as se mub 1~’ anr d coate LIw i t in o i l . .•\ f tc r a s semb lv a n d ~ mi o r to start i in g t i r e ii i’i ye nm r oto n’ ,a copious s u p p l y o f o i l was i n r i e c t e d i n t o t h e cup w in I c tine sp in-d le was r o t a t e d by i r an d . lii is was pe r Io mmc d to prevent nu n ” c h a n c eo f w e a r at s t a mt up due to l a c k o 1 1 uh m l c a n t . E a c h t e s t w a s ~~L’ 1’ —Io rnre LI min t i i a spa 1 1 o r wea r In i t o me 0cc t i n red onn t he s ~ i n d i eb a l l or to a p re—es tab ii sired t i inc U I ) . l o l l ow lung each muno t or St op —

page due to tir e vibi ’as~ i t c h , a l l h a l i s wei’e i n s p e c t e d . I f t in et e s t ball tr a il f a i l ed , t i r e t e s t w a s te m m mi i irate d . I f a s u p p o r t h a l 1m a d f a i l e d , all t ii r ee su p po u’t in a i l s we r’e r ep I a ced an n d t h e t e s tcont i nn u ed.

,-\ luhricannt meet i ;r g MI 1 — ! . — 2 3 t 99 sin e ci ficat l oin s w a s usedin a l l t e s t s and supp lie d at a r at e o f S — b d r o p s pe t ’ m i n u t e .Fir e sp i n d l e hal Is m~em e 1~~.5 nwi m r d i a m e t e r and t int ,’ Sii I’~b)0i’t hallswe re mac in i nc ~i I no iii M — 50 s t eel t o 1 2 . 7 mm miii di mmme t e m’ . The s i i n ~ di espeed am i d load , tine ca I cmi b a t e d nina x i n ’m mi un ile i’t St mess , a n d t h ecalculated Lundhe rg- Pal ung men

~~~ i i IL’ f’o m eac in test co u n Li I t i o n

nr sed ar€’ rresentc~i in Table 8.

Test R e s u l t s ami d I ) i s c u s s i o n

Tir e t e s t i m r g w a s i m n i t I znted on t i r e Ceral los’ 14 \’ balls win chIrad beeui finisined using a p r e v i o u s l y e s t a bi i s h n e d p r o c e d u r e ( 2 )c o n s i s t lu n g o 1 n’oughn 1 app i r ig m~ I t lr 1 5 ~inm LI1 an n onn d t o I towed by po 1 -

i s in i ng w i t i r F — ~3t) gr ade .\l (1 3. The sam e pr oces s was used tofin~,sh all tire ba t I s tested on i this program .

To pe n ’mn i t a di r ec t coimipa r i s onr between i t ir i s mate rial andp r e v i o u s ly tested Si 3N~ ha l b s , t e s t i n g w a s m i t b a t e d w i t i r al o a d o f 14 7 0 N ( 333 ib s) wl r cii r moduces zi m ax i u i u um m n lie r t : s t r e s sof 5 . 5 (Wa (800 K s i ) . A sp i nd l e ‘~p eed o f 10 ,000 rpm was used .Eon r t e s t mach i n e s we me us e Li on t n 1 s i ro g r’a in.

Sinortly after st: i u ’ tinr g tine test i mi g, e xcessive w e a r wasnote il by disco 10 n a t i on o I t i ne I oh r’ i c aunt win i cii t u m n r e Lib l a c k . S ince t ine w on r occ t im red w I t In I ir a sho i’t t e s t p en ’ j o dp o s s i b i l i t y o f t e s t macir I n c and lub n icat i omn p r o b l e n r s were coin —s i de red. There fo re , eacir imnacir i uie was c h e c k e d fo r’ alt gn r m enn t am r dpro j c r 1 oa d app I I c a t i 0 nr . I n n a LI di t i o nr co nip a r i sour ha 11 s t’roirr alot t e s t e d on a p r e v i o u s coun t r ac t ( 2 0 ) w e r e ruin f o r s e v e r a l iro um i ’s

* p r i o r to , and inn some cases I o l b o m % ’ i n n g , t i r e C e m a l l o v h a l l t e s t s .In a l l cases t i r e conmnpa ri sour b a l l mann w I t i n c u t wea i’ ; thus , i m d i —

c a t i n g t h a t the w ea n ’ failures were m a t e r i a l r e l a t e d .

RESEARCH LABORATORY 5KF IN D U S T R I ES. INC.

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AI ~~~ ’b ’057

C o n s i d e r i n g t h a t the m a t e r i a l n u u ay s t i l l he s u i t a b l e forb e a r i n g s , w ire re t h e I l c r t : s t r e s s w o u l d he l o w e r , ( t h e e x c e p t i o n -a l l y h i g h stress l oads a r e a p p l i e d inn t ine f o u r b a l l t e s t s t oreduc e the test time u ’eLluire nn ent ) tire il ert : stress value w a sdec reased in n s t e p s o v e r t h e r e m a i n i n g t e s t s to a minimum valueo f 3. 4 GPa ( 500 k s i ) . ‘b ’hre t e s t st ress , t e s t t i me , a n d res u l t so f eac in t e s t are p r e s e n n t e d j un ‘b ’ ab l e 9 . W e a r m a t e dec reasedw i t h load b u t w e a r n e v e r s t o p p e d c o m p l e t e l y even at t h e l o w e s ts t ress l e v e l . Tin s pre v e n r t e d o b t a i n n i n g c l a s s i c a l s p a l l i n g f a t i guedata on tin e m a t e r i a l e x c e p t p o s s i b l y inn two t e s t s whe re s p a l l i n gf a i l ure s o c c u r r e d w i t h mn i rn i n mna l wea n ’ ( T e st s No . C - l l and C — 2 0 )Wean’ at nun x i m u m l ie r t : s t res ses o I’ 3. 4 amn d 4 . 1 GP a ( 5 00 ~ t~0 0 k s i )was intermittent whereas it r~as c o n t i n u o u s at 4 . 7 and 5.5 CPa( t S O ~ 800 Ks i ) maximum l ie rt : st messe s , Inn t i ne i n t e r m i t t e n n tmode the r o l l i n g t r a c k w o u l d I i r st g l a:e aun d a c . ju i me a s h n i n e‘Fin e g la :e d m a t e r i a l w o u l d t i n e n n p e e l o f f s u d d e m i l v and t ire p r o c e s sr e p e a t ed i t s e l f . I t i~ns a l s o o b v i o u s d u r i n g t i r e t e s t i u n g ofCe r a l l o y l 4 ” Y h a l l s t h a t t ine w e a r w o u l d o f t e n i s t a r t as p i t t i n gor n n i c r o sp a l l i n g at t ine I i g u t c o l o r e d (g r ey ) ar e a s win i cii w e rer a n d o m l y d i s t r i h u t e d ov e r tin e s u r f a c e of tir e b a l l .

As a r e s u l t of t ine e x c e s s i v e wear e x p e n i e n n c e d d u r i n g t in er o l l i n g f o u r - h a i l t e s t s e v e n r a t t h e l o w e s t st mess i’a l ine s , tireCe t’z i l l o ” l i ” Y n m n a t e r i a l c o n t a i u n i mn L~ aco u s t i c n i u i c m o s c o p i c a l l vd et e c t e d po nos i tv 1 s un ot co n s i d~’ med t o be a good cam n d i da te f o rme 1 1 1 ii g he n r ’i ur g app I i c a t lo in s . A nr es t I uumn t e o I tin e i u r ine rent spa l —

I i n~ f a t i gue 1 l fe of t i n i s t ype 0 I ma ten ’ i a I canr be oh t a inc LI m o w -

e ve r liv us i n ~ on lv t i r e s i n a i I i in g Ca I I ore I i yes in ‘lest s C - 11 andceuni t l u g a l l o t h e r ’ t e s t s inn w i n i c i n w e a r o c c u r r e d as s u sp e n s i o n .

P r e ssu n-e l ess si n t e red hail s imnaLle by ( i l l : Sy 1 van ia we n .e t e s t € ‘dn e x t . T ire se b a l l s w e r e I i g l n t g ray iii c o l o r and c o i r t a i n n e d abou t2 v/ o ~ 0 ros i t v e ~‘enn 1~’ LI 1 s t mi hut e d t i n r o u g mn t i r e vol ume

The t e s t li n g of t irese b a l l s was al so u n t i n t e d at a St m e s sl eve l o f 5 . 5 GPa ~~00 N s i ) H e r t z st m e s s . bVea r was noted byt ire d i s c o l o r a t i o n n o f t i n e l u h m i c a n n t a f t e r ’ h nir i u r u t e s o f t e s t i n g .I in spec t ion o 1 the h all a ft c r’ one i rou r ’ o f r ’uum r n i n g 1, v i b n a s w i t cliset in i m n s e n s I t i ye pos 1 t i on to pe i’mi t r ’un nin i in g) showed that ap —

p u’ec jab it ’ w ea r a n d seve ral si~ r I I s m ad occur r rc d . Tes t l u n g waste r’m i n a t e d on ti n i s m a t e i’i a I a ft c r four add i t i ona 1 t e s t r’uns we rep e r f o r m e d w i t h i l c r t : s t r e s s v Z n l u e s as low as 4 .1 CPa ( b O O k s i )w i t h s i m i l a r r e s u l t s , 5 e L ’ T a b l e 10. P o r o s i t y i s b e l i e v e d to bep r i m a r i l y r e s p o u n s i h i e fo r tin e p eon’ r o I l i n g c o u r t a c t p e r f o rm aunceof t h i s lo t o f b a l l s . i u r t h e r e f f o rt i s h e i n r g made at GTESv I van i a to p r ’odu ice mo re f u l l y dense roug in s inh e res.

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A l 7 l O S ”

The tin i rd g r o u p o! ha u s tested r~e n’e mad e f rem - i \uiR,\ 1 . 1 l i iNC 1 32 S i 3 N nrat e r i a 1 . By me nuns o 1’ a I . 5 mm di a net en ’ ii i i in ~I m epu t in the as — p n-e s Se d h a l l 5 I t w a s p o s s ft ii ’ to or i emi t t h ese h a i l sso t h a t tin e track inte r ’secte d tine e q u a t o r i a l b . m u r d it t r~o p o i n t s .This allows evalu a t ioun of t ire r e l a t i v e t i t i gui’ su ieut gt h et tineh u l k and tine e qu a t o n i a I b a n n d m a t e m i a 1 s . Re ca e o I t he c a r ’l vw e a r f a i l ure e x p en ’ i circe ~I r~ i t ii t i e et hue r t m~ o ‘ :a I e mu a 1 s i es tedt irese tests we me m n t i a tCL I at a lie it : st me ~ s o 1’ - 2 . ~ (1’ a u SO k s I 1S I nce no wear fa 1 1 Lure s u~ e re curc o u:i t e m e d i n n I l i t ’ m u t u I tes t run g0 1’ tin is m a t e r i n I and tin e test t r nit ’ r eq :i L a o oh a i i i a spa 11was long at tine lo w er s t r e s s l ev e l , he l i i i ’ u~ 1 IL’ r~n~ ‘~ctat 300 inns . Tire lie r t : st me ss is as t I n c u r iii c ii ’ a~ i’d o S . S CPa

~O0 Ks I ) , and t i r e t e s t co in t i mi ne d out r 1 Ia r ‘~ l i r e 01 a t I me ti~’ 0 1

an additional 300 inoun’ s . I b i s in crea ’-i ’ in stress t~a~- p e r f o r mn r e dfor two p u r p o s e s I ) tIC t e in r u n t ’ 1 1 tire i n g i r t ’ F st mc s s Ic ye 1 m~ oul dresul t in wear as exp e r ’ i e nr c c d 1’ v l i e ot lie r m~ o cnn d i date m ate x’i n i s2 ) a c c e l e r a t e t i r e t e s t i u r g anr d keep c es t t I me i~ i t in i n t ine t i ncfn’ame of tine p rog ram . Tint’ t es t res m u I t s a ri j r e se u n t e ~i i n l a b le 11w h i ch a l so show s tin t’ ca l ciii a I eLI cii i i i va 1 c u t t e s t I i t’i’ at S S CPa(800 ksi ) lie i’t : st mess and t i r e tiieo ret r c .i 1 1. , i i m e .

S ince a l l t h e v a l u e s w e r e coins i ~ie n ’ed t o be q u i t e good t i n eN C l 32 m a t e r i a l is consi tie red to he super nom’ t o t i r e eti nci’ twot e s t m a t e r i a l s and is c o n s i d e r e d to he a good c a nn did n t e (e m’ro l l i n g hearing material.

l’he lowest test 11 Ic val uu e was 5 t i mime s t h e c o m p u t e d tineo-re t i ca l L~~ l i fe ann d tbn n’ee t r a c k s rain fo r’ miro n’e t i n a n r 33 t i m e st h e c o m p u t e d ~~~ life wi tin out failing.

E x a m n i nat I our of spal l e d N C I 52 h a l l s i’eve a l e d two types of

~p all inn it i at jour . A l 1 bu t one spa l I we u’e no r ’ma I fat i gue spa u s01’ t ine ty pe shown in h i gore 2 4 . I t i s seen inn I i gore 24 t h a tt re l ie r t : c r a c k s p redon n i nr a te at t i n e edge o I t i n e t rack and umn ovetowards the cen n te r ’ of tire track as t he n ’ p r o gr e s s . On t he 0th 1sin~I1 1 (Fi g u r e 2 5 ) tine hlert: c r a c k s had foruine d at t in e c e n t e r oft he t r a c k and ran p e r p e n d i c u l a r ’ to t i n e t r a c k . Tine s p a l l isseen to he houn L ied on one si ~le by a H e r t z c rack. Such ilert:c n’a cks , r u n n i n g p e r p e u n d i c u l a r to tire track , are fo n’ui re d byr epea ted c o n t a c t w i t h a sp a l l edge on tire s u p p o r t b a l l s . Innmost cases a s p a l l e d suppor t b a l l does riot cause t ine t e s t b a l lto f a i l due to t ine i n d e x i n g of t i re s p a l l e d reg io n o u t o f t inec o n t a c t b a n d . None of t ine s p a l l s occu r r e d in n t i re e q u a t o r i a lband reg ion i n d i c a t i n g ab sence o f s t r e n g t i r d e g r a d a t i o n inn t i n a tre g i on .

E xamination of tin e rolling track on a Ce ral1 o~’ 1471 ballshows m i c r o s p a l l s and wear’ d e b r i s particles generated tinatcaus e o i l di sco l o ra t ion d u r i n g t es t i ng ( 1 i gure 2 h )

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RESEARCH LABORATORY SI CF I N D U ST R I E S . IN C .

A L 7 7T05 7

In o rde r to p e r f o r m a d i r e c t co m p a r i s o n w i t h the NC 132material previous ly tested (19) the statistically evaluated L 10life of the NO RA LI DE N C 132 Si 3 N . ninaterial was performe d usingthe maximum likelihood t ec hnn i -,~ue . Tin e median unbiased L 10 lifeis presented in Table 12 along with the L 10 life of ~1-5O steelhalls and similar ly finished silicon nitride balls tested in (19).

Since the steel balls were tested at a lower Hertz stressvalue than the Si 3 N~ b a l l s a d i r e c t c o m p a r i s o n of the e s t i m a t e dL i 0 life va l ue s cannot be made . To obtain a relative evaluationof the two materials the ratios of their e s t i m a t e d L 10 life tocalculated theoretical life mus t be made . Tir e M- 50 ratio is0 .112 and the ratio of the NC 132 materia l is 4 . 7 2 . A compar i sonof these two value s i n d i c a t e s t h a t the NC 132 Si 3 N . out perfo rmedthe M - 5 O steel by a factor of 4 2 . A s i m i l a r m a x i m u m likelihoodan a ly s i s of the i n h e r e n t f a t i gue l i f e of Ce radvne 1471 is a l s og iven in Table 12 , sin ow i n g good f a t i gue p e r f o r m a n c e connpare d toM - S O steel.

It must be recogni:ed that tlne estimated L i o life resultsbased on small test group s are particularly sensitive to asin gle failure i f t in e re is r’.ide sca tter in individua l test lifedata. In addition , the ini g in contact stress levels used in ther o l l i n g fo u r - b a l l t e s t s , comp a re d to tine lower con t ac t s t r e s se sin ball and roller bearing applicatio ns , affect materials havin r gdiffe rent hardness ann d d u c t i l i t y , such as steels and ceramics ,in quite diffe rent was ’s . Th e re fo re , t h e l i f e e s t i mates o b t a i n edm ust he con s ide re d as i n di c a to rs o f l i f e an d no t as eng i n e e r i n g~‘a 1 ue s.

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RESEARCH LABORATORY 5K F IN D U S T R I ES. INC.

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A L 7 7 T 0 5 7LIST OF RE FE R I -iNCES

1. R o w c l i f f e , D. J. and Jorgensen , P. J . , “ S i n t e r i n g of S i l i conNi t ride ,” Pro ceedin gs : Worksho p on Cer ami cs fo r Advan cedHeat Eng ines , sponsore d by ERDA , pp. 191 , Orl ando , Fl o r ida ,(1977) .

2. Dalal , H. I’1. , et al , “ E f f e c t of Lapp ing Pa rame te r s onGenerat ion of Damage on Si l i con N i t r i d e B~~l1 5 ’ir fac es , ”Final Report , Naval A i r Systems Command Contracc N o.N00019-76-C-0147 , SKF Report No. AL76T026 (1976).

3. Rob are , ~~~~ W . and R ichers on , D. V. , “Ro to r Blade Mach in ingDe velopment ,” ARPA-NAVSEA/AIR IHSL\RCH Ceramic Gas TurbineEngine Demons t r a t ion Program Review , Maine M a r i t i m e Acade my ,Cast ine , Main e (1977) .

4. Timoshenko , S. and Good ie r , J. N., Theory of Elasticity,New York , McGraw H i l l (1951) .

5. ASTM Test #F394-74T , Annual Book of ASTM Standards , Par t43 , pp . 758 ( 1 9 7 5 ) .

6. J. B. Waxhtman , W. Capps and J . Mande l , “ Bi a x i a l F lexureTests of Ceramic Substrates ,” J . M a t l s . 7 , 188 ( 1 9 7 2 ) .

7. Kleiner , R. N . , GTE Sylvan ia , Ceramics Research Division ,Towanda , Pa. , Private Communications .

8. Baum gar tner , H 4 R. and Ri~zh e rson ,R .W., “Inclus i on Effectson the Strength of Hot Pressed Silicon Nitride ,” inFracture Mechanics of Ceramics , pp. 367 , Plenum (1973).

9. De rkac s, T., et al , “Non-Destructive Evaluation of Ceramic’s ,”Final Repor t on Nava l Ai r Development Cen te r Contrac t No.N00019-75-C-0238 ,(July 1976).

10 . Derkacs , T . , et al , “Ultrasonic Inspection of CeramicsCon tain in g Small Flaws ,” Final Report on Naval Air Deve lop-ment Center Contract No. N62269-76-C-0948 , ~1arch , (1977).

11 . McLean , A. F., et al , “Brittle Materials Design , Hi ghTempera tur e Gas Turbine ,” Interim Report No. 9, AMMRC CTR76-l 2 ,(April 1976) ,pp . 101.

12 . Kessler , L. W . , in Proceedin g of the Sympos ium on Opt icaland Acous tical Mi c ro -E l ec t ron ics , Vol. 23 , ed. A. Ol inerPolytechic Press ,(1974).

13. Bra tt on , R . J . , Anderson , C. A. and Lan ge , F. F., “Ce rami cRotor Blade De velopment ,” Elec tric Power Research Inst .ReportContract No. RP421 - l , ( 19 7 6 ) .

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RESEARCH LABORATORY ~~K F I N D U ST R I E S . IN C .

AL77T057

14. Baumgar tne r , H. R. and C o w l e y , P . E . , “Silicon Nitride junR o l l i n g C o n t a c t B e a r i n g s , ” F i n a l Report , A i r Sys temsCommand Contract No. N00019-84-C-0l57 , (1975).

15. Va lor i , R., “Rolling Conitact Fati gue of Silicon Nitride ,”Naval Air Propulsion ‘lest Center Report No. NAPTC-PE-42 ,(August 1974).

16. Dalal , 11. M., et al , “Surface Endurance and Lubrication ofSilicon Nitride Ball Bearings ,” Final Re por t on U . S.Department of the Navy Contract No. N00019-75-C-0216 ,SKF Report No. AL75T030 ,(December 1975).

17. Pa rke r , R . J. and : a r e t sky- , Ii. V., “Fa ti gue L i f e of Hi ghSpeed Ball Bearings wit in Silicon Nitride Ba-is ,” Tran s.ASME , J. Lub . Technology , 97 (3), pp . 3 5 0 -357 ( 1 9 7 5 ) .

18. Almen , J. 0. and B lack , P. 11 . , “ R e s i d u a l S t r e s se s andFat i gue Life in Metals ,” New Y ork , McGraw H i l l (19b 3) .

19. Letner , E l . R. , “Residua l Grinding Stresses in HardenedSteel , ” AS ME T r a n s a c t i o n s , Vol . 77 , pp . 1089 ( 1 9 5 5 ) .

20 . Residual Stress Measurement by X-ra y Deffraction , SAEHandbook Supplement i-IS 784a (1971) .

21. G a z z a r a , C. P. and Reed , D . , “A Computed X - r a y D i f f r a ct i o nPowde r P a t t e r n fo r Alp ina and B e t a S i l i c o n N i t r i d e , ” ArmyMa terials and Mechanics Research Center Report No.AMMRC TN 75 -4 , (A p r i l 1 9 7 5 ) .

RESEARCH LABORATORY SKF I N D U S T R I E S . INC.

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TABLE 1

DATA ON GTE SYLV ANIA POWDER

Type of powder: SN -502

Average par ticle size: 0.5 pm

Surfac e a rea : 3 . 5 iun /g

Oxy gen Con tent: 1.24 W/o

% Amorphous Si 3N 4 : 40

% o ~ - Si~ N 4 : 5 7 . 3

%.6 - Si 3N 4 : 2 . 7

SPECTROGRAPHIC CFIE i~1 ICAL ANALYSIS

Element Ap p r o x i m a t e

Percen t

Al 0 . 0 0 2

B 0.0008

Ca 0 . 0 0 0 8

Fe 0.001

Mg 0 . 0 0 0 9

Mo 0.01 (ND)*

Ti 0 . 0 0 8 (ND)

* Not De tec ted

RESEARCH LABORATORY SKF I N D U S T R I ES. I N C .

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TABLE 2

DATA ON S I L I C O N N I T R I D E POWDER USED BY CER A DYN E

Type of powder : AME CP85

Avera ge p ar t ic le s i z e : 2 . 5 pm

% ~~~Si~~N~~: 90

% ~~~~- Si r N~~: 10

Fr’ee Si : 2Oxy gen content : 2.1 w,0

Theore t ica l densi t y : 3.32 gm/cc

SPECTROGRAPHIC CHEMICAL ANALYSIS

Elem ent Approx. Elennent Approx.

Percen t Percen t ____

Si 5 8 . 0 Sr 0.035

Fe 1.3 Mo 0 . 0 2 8

Ca 0.34 V 0.013

Al 0 . 4 8 Cu 0 . 0 0 5 8

M g 0 . 0 2 3 Ti 0 . 0 3 1

Ni 0 . 0 6 9 :r 0.0022

Mn 0 . 0 3 7 W 0 . 0 7 ( N D ) *

Cr 0.015 Na 0.03 (ND)

Co 0.0045 K 0.10 (ND)

*Not De tec ted

RESEARCH LABORATORY SKF I N D U S T R I E S . I N C .

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TABLE 3

S P E C T R O G R A P H I C C H E M I C A L A N A L Y S I S OF NC 132

A l u m i n u m 0 .2 8

Calciunn 0.044

I ron 0 .4 6

Magnesiunn 0.56

Titanium 0.04

Tungsten 1.3

Silicon Nitride Balance

RESEARCH LABORATORY SKF I N D U S T R I E S . I N C .

AL 7 7105 7

TABLE 4

MEASUREMENT S ON I N D I V I D U A L ROUGH SPHERES FROM CER ADYNE

Run No. 1827

P/N Diame ter Hei gh t Densi tymm ( i n . ) mm ( i n . ) gm/ cc ’~ .0l

1 22 .1 (.87) 22.4 (.88) 3.30

2 2 2 . 1 ( . 8 7 ) 2 2 . 6 (.89) 3.32

3 22.1 (.87) 22.4 (.88) 3.31

4 22 . 1 ( . 8 7 ) 22 .4 ( . 8 8 ) 3 .32

5 2 2 . 1 ( . 8 7 ) 2 2 . 4 ( . 8 8 ) 3 . 3 1

6 21.8 (.86) 22.4 (.88) 3.31

7 21.1 ( . 8 7 ) 2 2 . 6 ( . 89) 3.31

8 2 1 . 8 ( . 8 6 ) 2 2 . 4 ( . 8 8 ) 3 . 3 0

9 2 2 . 1 ( . 8 7 ) 2 2 . 4 ( . 8 8 ) 3 . 3 1

10 22.1 (.87) 22.6 (.89) 3.32

11 2 2 . 1 ( . 8 7 ) 2 2 . 4 ( . 8 8 ) 3 . 3 0

12 22.1 (.87) 22.4 (.88) 3.31

13 21.8 (.86) 22.6 (.89) 3.31

14 22.4 (.88) 22.4 (.88) 3.31

15 22.4 (.88) 22.4 (.88) 3.30

16 22.1 (.87) 22.4 (.88~ 3.31

17 22.1 (.87) 22.6 (.89) 3.31

18 22.1 (.87) 22.4 (.88) 3.29

21 3 (.86) 22.6 (.89) 3.32

RESEARCH LABORATORY ~~~~~~ IN D U S T R I ES. INC.

AL 7 7105 7TABLE 4 (CONTINUED )

Run No. 1840

P/N Diame ter Heigh t Densi tymm (in.) mm (in.) gm/c cto.1

20 2 1 . 8 ( . 8 6 ) 2 2 . 4 ( . 8 8 ) 3 . 3 2

21 21.8 (.86) 22.4 (.88) 3.32

22 2 1 . 8 ( . 8 6 ) 2 2 . 4 ( . 8 8 ) 3 . 3 1

23 2 1 . 8 ( . 8 6 ) 2 2 . 4 ( . 8 8 ) 3 . 3 2

24 2 1 . 6 ( . 8 5 ) 22 .4 ( . 8 8 ) 3 . 3 2

25 2 1 . 8 ( . 8 6 ) 2 2 . 4 ( . 8 8 ) 3 . 3 1

26 2 1 . 8 ( . 8 6 ) 2 2 . 4 ( . 8 8 ) 3 . 3 1

27 21.8 (.86) 22.4 (.88) 3.31

28 2 2 . 1 ( . 8 7 ) 2 2 . 6 ( . 8 9 ) 3 . 3 2

29 2 1 . 8 ( . 8 6 ) 2 2 . 4 ( . 8 8 ) 3 . 3 1

30 2 1 . 8 ( . 8 6 ) 2 2 . 4 ( . 8 8 ) 3 . 3 1

31 21.8 (.86) 22.4 (.88) 3.31

32 22.1 (.87) 22.4 (.88) 3.31

33 22.1 (.87) 22.4 (.88) 3.31

34 21.8 (.86) 22.4 (.88) 3.33

35 21.8 (.86) 22.4 (.88) 3.31

36 21.8 (.86) 22.4 (.88) 3.32

37 21.8 (.86) 22.4 (.88) 3.31

38 71.8 (.86) 22.4 (.88) 3.31

39 21.8 (.86) 22.4 (.88) 3.31

40 22.1 (.87) 22.4 (.88) 3.31

41 21.8 (.86) 22.4 (.88) 3.3 ].

RESEARCH LABORATORY 5K P I N D U S T R I E S . I N C .

_ _ _ _ _ _ _ _

A L 7 7 T 0 5 7

TABLE 4 (CONTINUED)

42 21.8 (.86) 22.4 (.88) 3.30

43 22 .1 (.87) 22.4 (.88) 3.30

44 21.8 (.86) 22.4 (.88) 3.32

45 21.8 (.86) 22.4 (.88) 3.32

46 21.8 (.86) 22.4 (.8~~) 3.31

47 21.8 (.86) 22.4 (.88) 3.31

48 21.8 (.86) 22.4 (.88) 3.32

49 21.8 (.86) 22.4 (.88) 3.32

50 22.1 (.87) 22.4 (.88) 3.33

RESEARCH LABORATORY SKP I N D U S T RI E S . I N C .

-

~~_ _ _‘ _~~ _~~~~~~

‘~~~~~~~ ——-—--—~~~~~~ ____

A L 7 7 T 0 5

TABLE 5

MEASUREMENTS ON I N I ) I V I D U A L HOT P R E S S E I ) N O R A L I D E S P H E R E S FROM NORTON

Group 1

Ball No. Diame ter Hei ght

mm ( i n . ) rum ( i n . )

1 18.21 (.7 17 ) 2 0 . 0 1 ( . 788)

2 18.23 (.718) 19.96 (.786)

3 18.39 ( . 7 2 4 ) 1 9 . 8 9 ( . 783)

4 18 .14 (.714) 19.91 (.784)

5 1 8 . 2 9 ( . 7 2 0 ) 19 .89 ( . 7 8 3 )

6 18.57 (.731) 20.11 (.792)

7 18.14 (.714) 19.99 (.787)

8 18 .21 (.717) 20.07 (.790)

9 18.08 (.712) 19.84 (.781)

Group 2

10 21 .39 (.842) 20.57 (.810)

11 21.31 (.839) 20.52 (.808)

12 21.21 (.835) 20.68 (.814)

13 21.44 (.844) 20.50 (.807)

14 21.26 (.836) 20.60 (.811)

15 20.93 (.824) 20.45 (.805)

16 21.13 (.832) 20.42 (.804)

4

RESEARCH LABORATORY 5 K F I N D U S T R I E S . INC.

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RESEARCH LABORATORY SKF I N D U S T R I E S . I N C .

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RESEARCH LABORATORY 5KF I N D U S T R I E S . INC.

AL 77 T 05i

TABLE 8

\ A R I OtI S TFS1 CONDI TI ONS AP P L I E D

Sp i n d l e A p p l i e d M a x i m u m T h e o r e t i c a l L u n d b e r g -Speed Load I le r t : Stress P a l mg r e n L i o L i f e( r p m ) ~N/1h s ) (CPa/ ksi) (10 6 r e v s )

—~~~~~~~~~

10 ,000 1480/333 5 .5/80 () 7

10 ,00 0 4 . 7/ o 8t ) 30

10 ,000 b2 / 1 4 0 4 . 1/b OO 93

1O ,00() 360/81 ~.4/5OO 481

RESEARCH LABORATORY 5KF I N D U S T R I E S . I N C .

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RESEARCH LABORATORY SKF I N D U S T R I ES. I N C .

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RESEARCH LABORATORY 5 K F I N D U S T R I E S . I N C .

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M ateria l and Median U nbi a se-~d Median tJnhi asedP r o c e s s i ng L~~ Life Estimate Slope E stimate

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NC 132 h o t Pressed Bil let 36. T’O 0 .91

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RESEARCH LABORATORY 5KF INDUSTRIES. INC.

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