Tribocorrosion behavior of boride coating on CoCrMo alloy produced by thermochemical process in 0.35% NaCl solution

Abstract

The boriding thermochemical process is a favorable option to produce protecting layer in metallic alloys surfaces. This work presents the corrosion and tribological studies of boride and un-boride surfaces of CoCrMo alloy. These results showed that the boronizing process was produced with the dehydrated boron past at 850 °C for 2 h. This process generated CoB, Co2B, and CrB phases in the alloy surfaces and increased the roughness (Ra) value. The boride surfaces presented a hardness of 30 ± 3.7 GPa with lower corrosion resistance than the CoCrMo alloy in 3.5% NaCl solution in distillate water. The wear rate and coefficient of friction were similar for the boride layer at 2, 3, and 4 N in dry conditions, nevertheless the coefficient of friction decrease in the corrosive environment with a lower wear rate than the un-boride surfaces due to the formation of a tribolayer that protected the contact zone.