Tribological behavior of borided surface on CoCrMo cast alloy.

CoCrMo alloys are used in a wide range of applications because of their acceptable fatigue strength and corrosion resistance. However, CoCrMo-based components exhibit a deleterious effect of wear. For this reason, surface modification through ceramic coatings has become in a useful alternative to improve mechanical resistance. The main aim of the present study was to investigate the tribological behavior of a system of diffusional boride layers formed on the substrate of CoCrMo alloy. For this purpose, different boron diffusion heat treatment parameters were performed: 1223, 1248 and 1273 K by 6, 8 and 10 h, respectively. Surfaces were characterized using scanning electron microscopy (SEM), surface roughness measurement, micro-hardness testing, and X-ray diffraction. The tribological response was studied by means of ball on disc tribometer under dry-sliding conditions tracking their friction coefficient, mass loss, wear rate and surface damage by stereoscopy and SEM. Boride coating at 1223 K by 6 h showed the better wear resistance, increased it 6 times relative to the wear resistance obtained for the CoCr alloy untreated sample. • CoCr borided sample at 1223 K – 6 h increased 6 times the wear resistance in comparison with the CoCr untreated sample. • The wear resistant borided layer was correlated with temperature and time parameters of boronizing process. • The maximum hardness value achieved on the borided surface was 5 times higher than the hardness of the substrate. • The main wear mechanism was severe abrasion for the untreated sample and surface fatigue for the borided samples. [ABSTRACT FROM AUTHOR]