Role of Mo on microstructure evolution and dry-sliding wear mechanism of CoCrNi-based laser cladding coatings

Abstract

CoCrNiMo_x coatings were prepared on the surface of 1045 steel using coaxial powder feeding laser cladding. The effects of different Mo addition on microstructure evolution, micro-hardness, and wear resistance under different friction condition of the laser cladding coatings were investigated. The results show that there is a critical amount for Mo on the structural transformation of CoCrNi. When mole ratio of Mo ≤ 0.4, the coatings is mainly composed of FCC eutectic structure, and when the mole ratio of Mo ≥ 0.6, a large amount of hard and brittle laves phase of NiMo₂-type structure is formed in the coatings, which results in the increased in micro-hardness of the coatings. At the same time, the addition of Mo affect the dilution rate at the interface. During the wear tests under YG6, Si₃N₄, and GCr15 frictional pairs, the dominant factors affecting the effect of Mo addition on CoCrNi medium-entropy alloys are the amount of Mo-rich eutectic structures and the formation of laves phases. Additionally, hardness and surface state of the frictional pairs are also major factors affecting the wear resistance differences of CoCrNiMo_x medium-entropy alloys under different friction pair effects.