This is the third part of a three-part series that investigates the rolling contact fatigue initiation and spall propagation characteristics of three bearing materials, namely, AISI 52100, VIM-VAR M50, and VIM-VAR M50 NiL steels. Though there is substantial prior work published on the rolling contact fatigue initiation of these materials, little is known about their spall propagation characteristics after spall initiation. In Part III, 208-size, 40-mm-bore bearings are examined for changes in appearance of the microstructure as well as residual stress as a function of depth in the circumferential direction. The correlations between the experimental results from Part I and computer modeling in Part II are made.

No abstract

Material screening tests have been p e r j i i d with four candidateface (14), (15). Both VPD and carbobaceous vapor lubricavapor phase lubricants under rolling contact conditions at bearing tion have d~~~o n s t r a t e d temperature capability well beyond test temperatures of 370°C. The lubricants eualuated were t-butyl the limits for even the best Vnthetic liquid phenyl phosphate (TBPP), polyalphaolejin (PAO), cyclophosphame (X-IP), and PA0 blended with 15percent TBPP (PAO+). Factorial analyses were wed to separate the effects of lubricant; bearing steel, T15 vs. thin dense chrome-coated T15; cage material, AISZ 4340 vs. Monel 400; and ball material, T15 vs. NBD 200 S i & . Responselubricants. This paper represents the first of a four-part series inves tigating VPD lubrication for rolling contacts at elevated temperatures. It covers the initial bearing and lubricant evaluation using a ball-on-rod tester modified for high temperature operation. Part I1 will characterize the performance variabk includcd in the anab'yses were the bearingfiction Coeficient, if a vapor iubrication system using the same bail-on-rod testwear rate, and life underaccehated conditions. The type of lubricant ers. part 111 will use analytical surface techniques to investiwas sign@cant at the 90percent confidence level for all three response gate the lubrication and failure mechanisms of specimens variables, with the PAO+ and TBPP showing the best results. In generated in Parts I and 11. Part IV will investigate diffusion gaeral, bearing mat&als containing Fe showed improved perfomechanisms involved in the vapor deposition process. This mance over materials which do not contain Fe at the bearing surface.research was performed as a preliminary step before introducing the technology into high speed rolling element bear- KEY WORDSings intended for use in gas turbine engines.

No abstract

No abstract