Effect of boriding on high temperature tribological behavior of CoCrMo alloy

Abstract

In the present work, CoCrMo alloy surfaces were subjected to powder-pack boriding at 950 & DEG;C for 5-hour and 7 -hour treatment periods. The obtained boride layers were characterized with scanning electron microscopy, en-ergy dispersive spectroscopy, X-ray diffraction, nanoindentation and high temperature wear tests. Character-ization results show that boride layers are composed of CoB, Co2B, CrB and Co2MoB2 phases. Up to 4-fold increase is achieved in nanohardness values due to the boride layers in addition to increased elastic moduli. Increased surface hardness coupled with the high temperature stability of boride layers led to nearly 12, 7 and 10-fold increase in the wear resistance of CoCrMo alloys, worn at room temperature, 250 & DEG;C and 500 & DEG;C, respectively.