Micro-abrasive wear resistance of CoB/Co2B coatings formed in CoCrMo alloy

• New wear resistance data for cobalt borides were estimated by micro-abrasion tests.
• The wear coefficients were determined for CoB and Co2B phases.
• The wear-mode map was obtained for CoB phase.
• The two-body, three-body, and mix mode wear mechanism were identified in CoB phase.

New data for micro-abrasion wear resistance of CoB/Co2B coating was obtained through a ball cratering test. The coating was formed on the surface of a CoCrMo alloy using the powder-pack boriding method. The boriding process was carried out at 1223 K over 5 h of treatment resulting in the formation of CoB/Co2B coating with a total thickness of 28 μm approximately. Both hardness and Young's modulus profile through the cobalt borides were evaluated by Berkovich depth-sensing indentation using a load of 25 mN. The wear coefficients of CoB and Co2B formed on CoCrMo alloy were evaluated by a Plint TE-66 micro-abrasion tester using SiC particles dissolved in deionized water as abrasive slurry. The results demonstrated that the cobalt borides have wear coefficients higher than CoCrMo and improve their micro-abrasion wear resistance. Furthermore, a wear-mode map was developed to identify the two and three body abrasion mechanisms and the transition between them modifying the concentration of SiC in the slurry and the magnitude of applied load.