Microstructure and Properties of ZrC Enhanced Laser Cladding CoCrNi Alloy Cladding Layer

ZrC enhanced CoCrNi-based laser cladded coatings with different ZrC contents were prepared on the surface of low carbon steel. The effects of ZrC addition on microstructure, hardness and wear resistance of CoCrNi-based medium entropy alloy coating were investigated. The results show that there is a good metallurgical bond between the cladding layer and the matrix without obvious cracks and defects. The CoCrNi alloy coating without ZrC is composed of single-phase fcc structure. With the addition of ZrC into the coating, phase compositions of the coating change to fcc+ZrC0.7+Cr23C6+ZrO2 multiple phase structures. The grains of the coating are significantly refined, and the combination of grain boundary strengthening, solution strengthening and dispersion strengthening (Orowan) is realized, which effectively improve the hardness and wear resistance of the coating. However, ZrO2 produced by the combination of Zr in ZrC and O in the air also has an adverse effect on the performance of the coating, mainly because the presence of ZrO2 will cause the uneven distribution of particles in the coating and weaken the effect of dispersion strengthening. Therefore, when the content of ZrC is low, the performance of the coating is not improved. However, when ZrC content in the coating increases to 5wt%, more ZrC0.7 phase is separated out from the coating, which can effectively improve the performance of the material. The hardness (HV0.1) is (6379.8 +/- 147) MPa and the coefficient of friction is 0.161, which is much lower owing to the synergetic strengthening effect.