Effect of WC addition on microstructures of laser melted Ni-based alloy powder

Nickel-based alloy powder was laser surface melted on the surface of S45C steel substrate with laser beam. The effect of WC addition on the interface layer and microstructures in laser alloyed layer has been investigated by X-ray diffraction analysis, SEM and TEM. There are three zones in the laser alloyed layer. The interface zone is shown as a bright layer of single γ-(Fe,Ni) phase. After the addition of WC, the interface changes from flat state to rough state, and the primary arms have smaller cellular structures on the interface. Eutectic of γ-(Fe,Ni)+Fe23B6 in NiCrBSi sample changes into γ-(Fe,Ni)+Fe3B in NiCrBSi+10 wt.% WC sample. In this sample, the eutectic zone approximately 20 μm in width shows fine structure which may be caused by eutectic structure prior growth due to eutectic temperature decrease. The martensite in heat-affected zone is formed due to the decrease of the critical cooling rate.