Influence of WC Addition on Microstructures of Laser-Melted Ni-Based Alloy Coating

Nickel-based alloy powder was surface melted on S45C steel substrate using a C02 laser. The effect of tungsten carbide (WC) on the interface layer and microstructures in the laser melted layer has been investigated by x-ray diffraction (XRD) analysis, and by scanning and transmission electron microscopy (SEM and TEM) techniques. There are three zones in the laser melted layer: the alloyed zone, the interface zone, and the heat affected zone of substrate. The interface zone appears as a smooth bright layer of single (mu)-(Fe, Ni) phase that serves as a primary crystallization phase in the laser alloyed zone. K-S lattice correspondence was recognized between mu-(Fe, Ni) in the interface and martensite in the substrate. The size of dendritic crystals decreased and eutectic structures in the laser alloyed layer changed after the addition of WC.