Effects of tribo-film on wear resistance of additive manufactured cobalt-based alloys during the sliding process

Abstract Cobalt-based alloys are widely used in the fields of aerospace and automobile, whereas poor tribological performances under low-load sliding conditions limit their applicability. In the present study, three cobalt-based alloys with Al and Ni additions were fabricated by direct laser deposition, and their tribological properties were investigated. The friction tests were carried out by sliding specimens against GCr15 balls in the same conditions. The lowest coefficients of friction and wear loss were observed during friction tests of the 2Al alloy, but the 2Al25Ni alloy had inferior performances. Multiscale characterization methods were performed and revealed that the tribo-films are comprised of nano-scale oxides and amorphous structures, forming on the worn surfaces of the 2Al and 2Al25Ni alloys. Meanwhile, the amorphous structure generated on the top of the interface was observed to retain debris, which was helpful for the tribo-film generation. Compared with the CoCrW alloy, due to the high oxidation capacity, the tribo-film on the worn surface of the 2Al alloy was beneficial for lubrication and wear resistance. Although the thick tribo-film was formed on the 2Al25Ni alloy, the coefficients of friction and material loss increased, owing to the film was generated by high temperature. This work gives a better understood of the tribo-film formation and influences on wear and friction behavior, getting an effective method to improve wear resistance of cobalt-based alloys.