Laser Surface Alloying of Cr-CrB2 onto a SUS 304 Stainless Steel Substrate

SUS 304 stainless steel was laser surface alloyed with Cr-20 wt% CrB2 powders. Phases. microhardness distribution, microstructure, and wear behaviour of the alloyed layers were investigated. Results indicate that the alloyed layers were composed of austenite, martensite, chromium carbides, chromium borides and iron borides, improving the microhardness from 220 HV0.1 of the substrate to 1400 HV0.1 of the alloyed layer. The microstructure of the laser alloyed layer consists of planar growth dendrite at the interface, followed by columnar dendrite, and dendrites and eutectics at the core and top surface. Wear results indicate that the relative wear resistance of the alloyed layer was 18.76 times of that of the untreated stainless steel. The improvement in wear resistance was attributed to the combined results of the high hardness, the grain refining effect, the solution strengthening effect, and the distribution of the hard Cr23C6, Cr3C2, Cr2B and martensite phases.