to be presented at the International Conference on Pressure Vessel Technology and 1996 ASME Pressure Vessel and Piping Division Conference, Montreal, Quebec, Canada, July 20-27, 1996.

RESIDUAL STRESSES AND RETAINED AUSTENITE DISTRIBUTION AND EVOLUTION IN SAE 52100 STEEL

UNDER ROLLING CONTACT LOADING

Ricardo C. Dommarco INTEMA Univ Nac Mar del Plata Av J.B.Justo 4302 7600 Mar del Plata, Argentina

Krrysztof J. Kozaczek HTML,Oak Ridge Nat. Lab., O a k Ridge, Tennessee, 3783 1, USA.

JukJ 2 6 @gG o$.$i

Pedro C. Bastias George 1. Hahn Carol A. Rubin Mechan ica l Engineering Department , Vanderbi l t University

Nashville, TN 37205, USA

ABSTRACT Residual strlt5stf arc intrduced and modified during manufacturing

and dm by normal use. In chis papcr the changes in magdude and distribution o f d u a l strrssff . mending the Strain i n d u d bansfonnation of retained rustcnite arc examined. Tats were conducted on S S 32100 bearing stccl with different mcunts of ntaincd austenite in a S-bali-rod rolling contact fatigue machine. The t e s ~ ~ wcre aavlcrarcd by applying wdlu~ltrdlcd micro-hdenmons on the wear trick a d using rough MS. The magnitude and distribution of residual strrsses and retained austenite am measured using x-ray diE3t ion tcchniqucs. The contribution of the residual Strcym md amount of retained austenite to the rolling conmt fatigue life is analpcd.

1. INTRODUCTION The residual strrsses (RS) pmcnt in components to k subjected to

rolling contact fanguc (RCF) a n be introduced by d i f f m t thenno- mechanical treatments (Mscda and Tsushima. 1994; Bank. 1994 Voskamp, 1986). The sign and magnitude of strsscs are affected by a latgc number of variables such 1s geometry of the component, loading rate, tempcralure. lubrication. manufacturing techniques, h a t Ircjbntnb, etc. These strcssc~ arc altered by h e plastic deformation and stress or Strain induced phase transfonsaon which takes place under m ' c e k d s (Voskamp. 1994). The amount of retained austenite (RA) present in the

region under the raceway of bearing steels decrclxt due to the action of reputed cyclic loading (Tricot et ai., 1972; Voskamp et d.. 1980: Yajima et d.. 1974). The kinetics of martensite decay has becn relaud to the formation of dark etching rrgiont (DER) and later of white etching bands (WEB) (Vosiump et al.. 1980). These bands have been shown to be fonncd of fcnite micro bands separated by q'ons ofthc

martensitic structure (Swihn et al.. 1976; bsterlund and Vingsbo, 1980). M e compressive RS develop in the circumferential ( V o s h p et al., 1980. Zwirkin and Schlicht. 1981; Voskunp, 1985) and axial directions (Zwidein and Shlicht. 1982) w.r.t the m y due to rolling conat loading. M s h u r n vducs of compmsivc circumferential rcsidul s1rcsse~

ashighasd, = -jOO to -800 MPa(Voskampctal., 1980)and a', = 600 to -900 MPa (Zwiriein and Schlicht, 1982) have k e n reponed for w n u r prssucs of p, = 3 3 and 3.0 GPk nspectivcfy. These RS have ken uxd (Zwirlein and Schlichf 1982) to explain the prr~ence and orientahon futures of WEBs in bearing *IS. It has ktn observed (Schlicht et al.. 1988) that in stabrked @hitic) tearing steels the compressive residual -vary h n M initial d = -200 MPato d = -500 MPa aftcrN = 10' cycles. Hower. thesc steels do not present a significant amount of Rx among their m i c r o s ~ c t u d anstituents. Work conducted in p&on_pan made out of (i) mbonitrided-d quenched. and ( i i i &nitrided-oil qucnchcd-shot-pccned inarcrial.% with 30-35!'* and 5-7% R.4 at the suriace respectively, revcalcd that the progrrssivc RA tnnsfotmatron into martcnsitc(y-a')is notdimtty coupled with the variation ofRS pat ina et al.. 1994; CYtanhola Batista et d.. 1993). The former vanes si_unificanfl\ during the fint 30 hours of operation and the latter has reached a stcad: state before tive hours of tcsting. Eventually. though. a shakedorvll narc (Johnson and Jcffrics. 1963) is reached

2 EXPERIMENTAL PROCEDURE 2.1. Rollina Contact Fatiaue Exwriments

RCF ta ts wcre conducted in a MI-rod rolling contact fatigue tester (Gtover. 1982). The standard thm Ws and s nrainer arrangement w3s rcplaccd by five balls without a retainer (Liston. 1993). AS a consequence of this change the number of stress cycles per revolution of the specimen increased from 2 3 9 to 3.98 ~y~leu'nv. The 9.53 nun (38') diameter spccirn.a rotaks at 3600 rpm and is lubricated by 8-10 drops per minute 0fExxon 2380 hrrbo 03. The mataisl uscd for the evaluation was sttcl SAE 52100; Table I indicates its chemical composition. TjMe 11 show the d 8 m t hQt &cabncnk applied to the specimens, and the resulting surface

Thc specimens wcre loaded by SAE 52100 rough balls (RB), ix. dia rarghnesr 0.1 1 pm (428 AA). The tests were conducted at a p k pressure of p, = 3600 MPa Acwrding to HertZan (elastic) theory this pzssuz produces an elliptical contact patch with minor and major contact k n g h equal lo: 1J= 3 13pm. and 2b= 5 4 9 m . mpcctively. This giva a

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rrfslxn a&() 57 md \ky used to dculatc the minor axu 21. by measuring the major c o n u t length Ib. which coincides mth the wcjr tnck wdth. The myor uos. tr;Ulsvme to the rolling dirtchon (RD). w a ~ m a s u r d to be Murid I b 650 pm for dI samples at 10' conuc&. and the minor mS. oriented in the RD. was estimated to be 23 570 pm. The operahng tcmpenrm of the balls-rod ysembly was rnaurcd as T = 75'C. ,Wed ikfccrs (AD) ~m plsccd on the w a r tnck by using a RockwcllC indentor, the load was controlled to produce uniform hcmisphcrical u r d c n m wth I20 pn diamcrm. The presence ofAD on the wear track sccclerarcl rhe qualimtivc evaluation of the RCF propcrda of materials. The specimens w r e loaded untll failure, i.e. spalling. took place. The tests w e r ~ automadcally stopped once a ccrtain vibration threshold was detat td by an d e r o m c t e r . A totaI of ten WE w r c conducted over each sample. The fatigue test results were ylalyzed ruing a two-parameter Weibull stahstic m d the L,, and L, lives were evaluarcd.

2.2. X d a v Measurements A b t a g +axis gmomctcr with the x-ny tube o p t i n g a 45 kVJ40

mA and Scintlg solid state detector were used for the measurements. The radius ofthe focusing circle was 290 mm. The incident x-ray beam uas collimated by a double pinhole collimator with 0.5 mm aperture and a divergence of approximately 0.1'. Cu K, radiation was uscd for the RA measurements. Cr y radiation was used for RS measurements. The gomomem was aligned snd calibrated using LaB, powder (MST SRIA 660). All @s were fit uith a symmetric P a w n VI function with 9 linear background correction and no Lorenu-Polarization-Absorption correction using the Scin- DMS ZOO0 sofhvan, Rev. 2.90. The least- squart estimate of proGle fit to LaBI powder pcak in the range of 9 tilts from -15 to -45' was bcner than 0.002' of29 (8 is the B r a g angle).

2.2.1. Retained Austenite Analvsisl The retained austenite content was detcrmirted by an x-ray d m t i o n technique on selected w u r tacks Ydiffircnt depths. Since chromium radiation could not be uscd. due to the &e wiidrh of the diffraction pcaks, Cu & radiation and a cjindncal collimator O.Smm in diameter m d 10 cm in length were mployed. This dhnm pcnemtcs approx.imately 1 .5 ;im (63% of the informahon comes from this hyx, which is known as the r penetration depth). For the analysis. the (200) austenite peak at approximately 3 = 75' and the

mmleMte doublet (2 1 I X I I f ) at 2e - 82' wcrc u&. A scan of 6' u;ls donc m d u c h pcsk wth a 33 stcp of 0.05' and a collechon time o i :.; sccocldr.pnt The analyis of retained austenitc was umed out us~ng ~hc algorithm k n b c d m (Cullity. 1978).

2.2.2 Residual Stress Measurements/ Residual s m measuremenu in h e martcnntc were done on all w a r tracks at diDfcrtnc depths ( s d a c e rnatcrisl wu sequentially m o v e d by chemical crching ;n 85 pn~ of distilled water. 10 pa- of hydrofluoric acid and 15 parts sf hydrogen pcronde). The S t a n d d Chi-tilt (NOW and Cohm, 198-! tshniquc wbs used with 7 equi-sin% tilts from ~ 4 5 ' to 1~r-45' in tuo perpendicular d k h o n s ( h o p and axial). Cr K, radiation w u & poyiding fora r penemhon depth 014.5 Am at Jro'. The 28 position of the martensite (21 1-1 11) reflection was appro.&ately 155.5'. and the peak width wbs appro~mately IO'. A 28 range from 150' to 161' U ~ S

scanned with thc step size of 0.06' and data collection times of 1O-iS secondsrtcp.

The least-squares profie Gt estimated error in 28 due to the counwg .d&s ws in the range 0.03-0.09'. A plane mes~ (biaxial) condihon uaj assumed at crch tested depth. and the unNtSSed lattice spacing do *as calculated using the Hauk-Ddle method @Ue and Hauk 1977). E e comccmcss of the d, value was vcnfied by calculating the indepth NCS component (0,3 which should vanish if the plane stress condition ;s sat iskd . The -main an+& w a ~ done using the classic Haci ' j dsoridun ( m e t d.. 1982). The stms convmion w s wried out u s q M ehsx modulus ofE410 GPa and Poisson's ratio.rO.3. The Cstimsrcc sradard d e v i a h ofRS and strains was calculated foUo*ing the procairn hi in(Rudnik ad coheh 1986). The RS wtn not conected for h e mafQiaf ranovaL The possible effect of sample geomeny (curvature of&: cjindcr> on thc pcak poSih'on, m d thus RS. was tested by aka? mcasurcments on a strcs-fnt sample with an identi4 game@. The mss-frtc standard was pnpand by painting a I00 dm thick hyer of:kx powder (pardcle sue =low) on a 9.53 mm (318") dimern Teflon A The m u s u r d on this standard were pnct idly 0 (within the m- ban).

3. RESULTS Figure I show the m-dual strcss distribution 3s a function of

Nomenclature:

A I = SAE 52100 cabonitredcd. high austenite AC?, = SAE 52 100 carbonitrcdcd. hi& a u t + cabides AD = artificial defects DER = dark etching regions E = elastic module Li, , L, = l iva @IO and 50 $6 failure probability mpcct N = number of contact or stress cycles R4 retained austenite RAT = retained austenite transformed RB = rough balls RCF = rolling contact fatigue RD rolling direction Rs a residual stresses IUII = S i G 52100 sample. tcmpcred@240'C

WEB = white etching bands a = scmimior axh of the contact ellipse b = semimajor axis of the contact cllipw d, = unstrmed lattice spacing p, = peak contact pressure F = cornlation dcgra bo = residual stress increase p = Wabull slope y - a'= austenite into martensite transformation 8 Brasg angle d-rrsidualstrcsses dc - Circudercnb'al residual strrtses q, ; us ; q3 - drcumf.. axial and normal stmscs r = pentbation depth v - P h ' s ratio f - tilts for RS rnevurcmcnts

depth for specimens ppc Rm. A I d ACI in the unworn state. u,, corresponds to the r d strases (along the axis ofthe specimen) and a, comaponds to the nrcumferenhal stresses. These RS uc due to the h a t treatment ad gNlding opcnhons. The maximum surface RS e q d to: a ) u , , = -570 .Wianda= ~ - 3 6 8 ~ ~ f o r s p c c 1 m e n R m . b ) ~ , , 1-473 ,MPamd as = -361 .MpI for spccimcn Al . and c) a,, = - 518 &(Pa and = - 398 &Pa tbr specimcn AC2. Also shown in fig. I arc the initd RS for u m p l a RI and Rn wth all - -548 MPk a, - -262 MPa and qi * 4 7 9 MPa. a, - -277 MPz rcsptiwly. The mqnitude of axial residual stresses was higher than the cucumferential stresses at the surface for all samples and at 35 pm for FUII and JO pm foc A1 and AC2. The amount of RA at the surt-kce was -3.6, -38 and -20% for spccirnens Rm A I and AC2. rcspccavdy. At a depth of75 the &Gal and the circumfercntral s t x t s a have hlmcd lcndk for all the materials. The tcnsile stress scan to cxtcnd decpa into the sptdmen typc RIIL and return to compressive at 150 -rn for A1 and A C . Emx ban for RS measurements have an average value lowef than 80 MPa for both a,, and an, and for most ofthe tcsts this value was much lower (appromatcly 45 MPa).

Figures 24 show the variation ofthe RS components a,, and a, in sp.cimaU RJJ& .4 1 d A C . This is showed as a function of 1x1 e x p d by N. the n u m k of contacts or loading cycles and for ditfcrent depths. i.e. d = 0.35.80.1JO and 200 -m. The present work has concentrated on the phcnomcna taking place near surface regions. One can observe the build up ofthe wfg, mmpmsive RS with the number of cycles. For specimens

a change towards :ess ixmpmsive sut-hce RS is obscn-cd. This behavior is cxpaienccd by bo& the higher axial &dual stress. ail, and the circumferential NCSS. 0,. The Epecimens type Rm shrJw a continuous increase of the axial compressive strests at the surface, and the circumferential strcsm show a decruse starting at N - 105. The RS at depths higher than - 140 rrm (refer to the kcys in Figures 24 ) arc considerably lower in nqnitudc and tmsile. i.e. a,,, ax s 100 ,MPa

Figure 5 show thc volumetric fraction of RA prcscnt at the surface in unworn specimens t ) ~ RL RE, RlU, A1 and AC2. For the carbonitridcd r p a k i.c. A1 and Ac?,. the amount of RA is also shown at -10 and 100 um. The R;\ confcnt at the surface for the tempered sapximens Q RII and RUI was uniformly low and approximately equal to 8. 16. and 3%. respectively. Figures 6 and 7 show the amount of retained austenite transfonncd (RAT) a a function of life for specimens bpe A I and AC2. and atdiflrircnt depths under the wear tracks. The RA decays very rapidly a[ the ~k and tien h e s approximately constant at around N = 10' cycles in specimen tlpe Al. and N = IO' in spccimcn type AC2. The hansformatiOn at LOO pm is higher than at 40 pm for A I and AC2. but in both cases are fu from complchon. reaching a maxjmum for these tests of near 50% 3t N = ~o'contsfts.

Figures 8 show the results ofWcibull analyws. i s . faiiure probability versus life of the RCF experiments. of specimens type RL RII and RJD. Figure 9 presents similar analysis for specimens type AI and AC2. These results are summarized in Table III which shows the L,, and L, lives. p - the WabuII sloopc. and i- the degrec of conelation. In all caxs the Wcibull slopes weft l o u n than 3.3, which is similar to the rcsults obtained with smooth. unindcntcd specimens (Glover. 1982).

t ) ~ X 1 andAC2 h ism inCrras~h the FS up to N - IO:. At this point

4. DISCUSSION The larse compressive RS observed at the surface of unworn

mytcnsiljc baring stock. sa Fig. 1. result from manufactuting o p t i o n s . Thc m i d u d strcss vs. depth protila due to heat treatment and grinding indicae that thc hoop streSSeS (ad arc shificd by approximatciy 100 MPa

DO& lar mp-cssve Val= Thrs diffcrcncc diminsha with deprh and disappean at 3mund 80 pm. It has ken s h o w h t this etfect is rrduccd by shot w n g which has IW) directional effect (Castanhola & h a et ri . I993).

has long h wribcd 'D the volumcmc change lssociated mth the N+u-assistc&'strain-indw y-a' msformation (522). nus lrdnsformauon has been i n d i c d to j, accompanied by a 3 - 4% ( 5 . 3 ) volume cxpanslon. and it has btcn csrimated(twm d d.. 1987) that a complete trjnsformation in 3 sral aifi a 12.5% nwned austenite content may result in an i n c r w in he comprrssivc d u a l stress lcvd ofup to a' = 400 m a Our obwrvaaors indicate that in the specimens type Al. the tnnsformation at the su& appean to have satuntcd at I kvcl of7S"r; this could be due to high 3.4 stability. and also R S which increase the energy necessary to drive -sic tm.sfmobn. The surface RS for this m a t e d incrcve ( A m - 500 hip3 I up to N - 10' cycles. declining thcrea3cr. Specimens type Act. w t x h show an i n c m in the RA mtent with depth, i.e. -20% at the s u r r k VQRU -39% at 100 um for the unworn condition. show a smaller i n c w in the RS s the surface (AP - 300 mi) up to N - 10'cycles d e c h q alter this value. This Iowa incruse in RS may be due to a l own D. content at the surface in the unworn condition. The percent ofRAT as a function of the number of c y l a follows the pattern observed for A: spccimcns. but in this case reaches 85% of bansfomcd RA at the surface Similarly. specimens of t ) ~ RtLl with the lowcst percent of RL\ st k: s u h . i e . -4%. show yr in- (ha= - 150 m a ) in the surface RS :: to N - i@ mont3crs. at around N - 5x16 contacrs. 50% of the X4 3 transformed

Thc vdumcbic change producal during the decomposition ofthe U contributes to the genedon of wmprcssive residual stresses. T!x contribution of this phax musformation to the RS build-up is not hu? relared to the RA content. and may be of similar magnitude to the S gcneratcd by inhomogeneous kinematic-plasa'c deformation. Spccimrrs with a h q c diffcrrnce in their retained austenite content such as 3Z (-4%)d.\l(-3%& we subjaxd to similar changes in the surface hoc? RS. Ao= - 2.50 MFb for RIJI versus Ao= - 380 MPa for AI. The d a m - in magnitude ofRS observed at higher numbers of stress cycles. i.e. ?; : IO'. may be the mult ofsoArnin3 due to a decay ofthe manensite. w k t produces a net reduction in the volume (tensile strwia).

The wbrdridcd -XI and XCZ. show higha RA conccntnbczs at the surt'sce. i.c. -38 and -20% mpcctivefy. Their L, liva arc hiGc than thost measured in the tempered specimens. h o n 3 these. k: specimens ~ p c RII which have the Iarsat L, life. i.c. Lso = 19.17~10'. also thc axs with ttre highest content of RA at the surface. i.e. - 16%. ihc presentwork agrees with urly observations (Macda and Tsushima. 1%. Glover, 1982) in that that would be a direct correlation bctwcm 5: percent retained austenite and the RCF.

Even though RA transformation and RS dcvelopmcnt are appamd! notdirally coupled. both contribute to RCF life enhancement It has h shown (Bruszcit 1984; Harris. 1999,) that compressive Rs arc benetid . whatcva their nature may be. On the other hand RA when nct transformed is present as a fme m i x a n with martensite enhancing the materid toughness. This may bc the most imporrant knetit of RA since RCF life w roughly doubled when comparing AI or AC2 against RIU lives, whiie thc incrtvc in RS arc ofthe similar magnitude.

The subsequent evolution o f t h e

5. CONCLUSIONS Thc hcat &eating pnrtsscs applied to SAE 52100 stccl rods (Tabk II)

resulted in diffncnt distributions of RS snd RA in the subsurface regions

cup u) 200 pm) The RCF induced the rnicrastmctud c h m g a (austenite to martensite transformatton) and the Rs distnbutlon at dl tested depths under the surt*ke

The residual s w vs. depth profiles due to thcrmomechuricsl m a t for cYborutndcd samples A I and ACZ were h o s t i d a t i d . The hoop m d ~ x j d spasa shoucd the same distnbutlon. With the hoop strrsses shflcd by approumatcly LOO hip3 towarb the less comp&vc values. fhe tempered samples (e.g.. Rm) showed different stress profiles but had the same magnitude of compressive stxsscs at the surface as the cubonitrided samples in the range 4 0 to -600 MPs.

The rolling amtact deformanon induced the bansformation of IM and d t c d in the distnbution of stresses in the subsurfacc regions. Rolling contSct cycling up to N 3 IO' q c l a i n c d the magnitude of mprcssive nrcssc~ at the surface; further cycling multed in lowering the compressive m d u a l SUCSSCS. The nte~ of incrcw and the subsequent dccrcase o f s e c s ~ s *ere higher for the urbonitrided sampla as cornpard wth the tcmpend ones. The sucsscs at higha depths (above 80 pm for the tcmpcrcdRmyxlabove40pmfforthcurbonitrrdedAI and AC:! samples) do not change sigdkandy with the number of cycles and oscillate in the

Carbonitriding resulted in higha volumetric fractions ofRA than the tnrr@g process. Samples of type AC2 showed a lower RA content than A1 at the surface but at higher depths (approx. 100 prn) both types of samples had the same RA content (3530%). The austenite 3t the surface of A 1 and AC2 mnsformed at high ram and rcached a stable level after 10'-107 qdes %tien SO% oithe RA was transformui. he transformation kinetics were ditfcrent for different depthr. the transformation fate was higher at 100 prn below the surface than at 40 pm. This is in agrumcnt with the locatlon of the most unfavorable s h e s fiesscs assisting the tnnsformation sround aZ=W pm.

The carbonitndcd samples A I and AC:! showed the highest fatigue sta an^^ They had the same distribution and magnitude of compressive residual stnsscs in the surface regions. A I showed a suw-or fatigue rrsiStanc~ which was attributed to the highat volumetric fraction ofRX at the surface.

The ukonitriding p r c c m for manufacturing of the A1 sample proved to be supcnor in that it provided for the highest resistance to RCF failure.

range of-200 to '00 m a

6. ACKNOWLEDGMENTS The authccs would Wre to dunk Dr. John Bewick and Aidan I<&gm

tiom SKF for providing the specimens used in the present research cffofi Thanks arc due to Mn. M q - J o e Liston from NTN-Bower Cop. for westing the w oithc 5-ball-rod tcchniquc. Mr. Ricardo C. D o m m m v,ould Wte to acknowledge the support provided by B. F. Lantos and Mr. 0, Qurroga from the Ccntro iugentino de Tribologia Partial funding for this project was provided by the National Science Foundation. This project was partially sponsored by the Assistant Secrehy for Energy Efficiency and Renewable Energy, Office of Transportation Technologies, as part of the High Temperature Materials Laboratory User Program, Oak Ridge National Laboratory, managed by Lockheed Martin Energy Research Corporation for the U.S. Department of Energy under contract number DE-AC05-960R22464.

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Swjhh H.Bcckcr. P. C.. urd Vngsbo. 0.. 1976, "M3rtcnsite d m y during di m h c t claguc in baIl butings.",Lfdalt! frons. A. vol. 7 k

pp. 42543'.

HM). pp.107-134. .4SM PhJadelphk

pp. 1099.1 110.

Quorlcrly. Vol. 12. pp. 3947.

Tncot. EL Monnof J. and Lluansi. M.. 1972.'LHuw microstructural alterations affect faugue propcrtes of 52100 tccd.".iieds Engmeermg

Vosksmp. A. P.. 1994. "Rolling contact fabque urd the significance ot'mdual strcssu." Proceed. 4th. Inlernar Con/: on 2esidual Speses. pp. 913-915. June 5-14 Baltimore. USA Published by the S o c i c ~ tor Experimental Mechanics (SEM).

Voskamp.A P.6ncrlund.R.Becka.P. C.. md Kngsbo. 0.. 1950. ' G r d d change in residual stress and microstructure dunng a n t s t fatigue in b d bearings.",Uelals Technology. Vol. 7. pp. 1621.

r

C Si P MO Mn Cr

0.75 - 1.10 1.0 ma. 5 0.015 0.5 max. 12 ma% 0.5 - 2.0

V-p.A. P, 1%5. %bkd rrspon~e to dling cuntact W i g . " ASMEJoumaf or/Tnbology. Vd, 107. pp. 359-3615

Yljirm. E, Miyrzrb'. T.. Sugyunr, T.. and Temjima, H.. 1974. "EE'ests of retuned austenite m the rolling fatigue life of bearings w." Trans JLU, Vd. 15. pp. 173-179.

Zwricin. 0.. a d Schlicht. H. 1982. "Rolling contact faclgue mechanisms - acceiaated k d n g versus field p e r f ~ t ~ n ~ ~ ~ . " Roiling Contact Fatigue Tuhng of Branngs - ASlMSTP 771 ( ed. Hamrock B. J. and D o w n . D. J.). pp. 358-379. ASTM. Philadelphia.

Fe

w.

Surface Hardness HRC'(Xn0op 500) Specimen Heat Trutment ID

RI IMartrnsitic hardened -tern@ .B 160 'CI1.5 hrs. 62.5

RII Martensitic hardened - tempered 8 100 "C11.5 hrs. 60.5

Rm Martensitic hardened - 'mpcrrd 9 240 'U1.5 hrs. 58.5 .- I

Martensitic hardened and tempered 200 'G'1.5 hn. Chrbonirrided @ 7W-930 aC'l-IO hrs in an atmosphere with a C activity betwetn 0.9 and 1.1 and a N potcntlal bcnvm 0.1 and 0.6% N

A1

RI 14.98 26.90 31719

RII 14.10 29.17 2.5526

Rm 10.93 20.00 32211

A1 18.79 46-90 2.0293

AC?, 15.43 35.59 22548

65i(850)

0.9194

0.8617

0.%35

0.79 14

09594

Table Et. S u m r n v of the RCF tests on S A E 52100. c I Life x (IO' cycles) I Weibull Stope I Conelation Factor I i P

DISCLAIMER

This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsi- bility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Refer- ence herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, r m m - mendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

I - -I--_ -----_ ~

- - - - - - -^__ --__c_________ - - _

6 a 5 n a 0 L

. . . . . . . . A .. 0 a&R'? ............... i ..1

4'00 ' 0 50 100 150 200

Cepth - pm Figure 1. lnrtial R S (unworn) as a function of depth for the three matet ie studied by x-ray diffraction: RIII, A i and AC2. Atso RS at surface for samples RI and RII. Refer to Table II for heat treatments.

Figure 3. Residual stresses as a function of Gfe for the A1 specimens. RS u,, (axfall and (long.) are shown for dierent depths: 0 urn (surface), 40 pm, 100 pm and 150 pm.

300 Specimen Type Rlll I

0

-300

2 2 400 2 5 !lj -900 - 0 v)

I2 .1200

-1 500

-1000

I - 1 .. .... -. .............. ..- ....... ...I. I

i

I I I 1

18 1oJ 1v 10J 1 0 10' 1 6

Life - # of Contads

Figure 2 Residual stresses as a function of He for the Rlll specimens. R S u,, (a-ai) and 9: (long.) are shown for Merent depths: 0 pm (surface), 35 pm, 80 pin, 140 pm and 200 pm.

300 1 SwcimenTypeAC2

Figure 4. Residual stresses as a function of life for the AC2 specimens. RS a,, (axdl and (long.) are shown for dierent depths: 0 pm (surface), 40 pm, 100 pm and 150 pm.

'* . u I

i

! 80 4

i I //- / ! i ..

a

5 * ............. ...............-- . . . . . . . . -.. . . . . . . I A I i

0 J o 20 u) 60 a0 100 120 100 10' lo, lot 1ff 1 6 1ff 10' loc

Life - X of contacts

Figure 7. R e t austenite bansformed i# a function of life for the AC2 sample at different depths 0 pm, 40 pin, 100 pm. The maxjmurr RA content at each depth. see Fg. 5. s used as a reference.

Figure 5. Initial RA (unworn) as a function of depth for materials RIII, A1 and AC2. Also RA at the surface for samples RI and RII. Refer to Table II for heat treatments.

I 1 I e A I ~ O - I

100 ca . .

r a L

3

2

1 ra

Lie x IO' (Contacts) 100 io1 11-9 I@ iv 16 io io7 io

Life - t of contacts

Figure 6. Retained austenite transformed as a function of life for the A1 sample at dfferent depths: 0 pm, 40 pm, 100 pm. The mw*mum content at each depth, see Fig. 5, is used as a reference.

Figure 8. RCF failure probaM2y as a functjon of life for the converitjonaW heat treated samples: 0 RI. tempered at T = 160'C: A RII. tempered at T = 200'C; 0 RIII, tempered at T = 240%.

, ' : i : / , . ... ?? !

- 3 L22 :m

Life x 10' (Contacts) Figure 9. RCF failure probability as a function of ffe for'the carbonibided samples: 0 Ai , carbonitreded (high austenite) and A AC2, carbonitreded (high austenite + carbides).