Influence of Ta strengthening on microstructure and wear resistance of laser cladding Ni45 coating

The experiment is to gain laser cladding complex Ni-based coating with excellent wear resistance and without defects, by adding 5wt.% Ta into laser cladding Ni45 coating. This paper researches the influence of Ta on microstructure and wear resistance of laser cladding Ni45 coating. The results of the experiment show that strong carbide forming element Ta preferentially react with element C to generate the TaC hard phase, which restrains the growth of coarse primary carbide M7C3 and the eutectic structure of γ-Ni⁺M23C6, refines microstructure of the coating, reduces the cracking susceptibility and then gain the laser cladding coating without defects. The mircrohardness of Ni45+5%Ta complex laser cladding coating improves by about 18% compared to Ni45 coating; and its abrasive wear resistance improves by about 20% in dry friction environment. The solid solution strengthening formed by Ta improves the resistance to plastic deformation of Ni matrix. The refined crystalline grains restrain the nucleation and expansion of micro cracks on grain boundary, which prevents materials from falling off in form of grain. In addition, the primary generated TaC has higher mircrohardness than M7C3 and it disperses in matrix, which in some extent impedes the cutting motion of abrasive, consequently, being conductive to improve the mircrohardness and wear resistance of laser cladding coating.