ROLLING-CONTACT FATIGUE PERFORMANCE OF DETONATION GUN COATED ELEMENTS

Rolling contact fatigue performance of thermal spray coatings has been investigated using an experimental approach. A modified four ball mac hine which simulates a rolling element bearing was used to examine the coating performance and failure modes in a conventional steel ball be aring and hybrid ceramic bearing configurations. Tungsten carbide (WC- 15%Co) and aluminium oxide (Al2O3) were thermally sprayed using a supe r D-Gun (SDG2040) on M-50 bearing steel substrate in the geometrical s hape of a cone. A coated cone replaced the upper ball that contacts wi th three lower balls. The rolling contact fatigue (RCF) tests were per formed under immersed lubricated conditions using two different lubric ants. Fatigue failure modes were observed using a scanning electron mi croscope. Microhardness measurements of the coating and the substrate and elastohydrodynamic fluid film thickness results are included. The results show the requirement for significant optimization of the coati ng before use in rolling element bearing applications. The coating was fractured in a delamination mode. Test results show an optimization i n coating process is required before these coatings can be used for ro lling contact applications. WC-Co coatings perform better than Al2O3 c oatings in rolling contact. Copyright (C) 1996 Elsevier Science Ltd