Research on vacuum brazing MCrAlY-Cr3C2 coating on single crystal superalloy

MCrAlY-Cr3C2 composite coatings were prepared by using vacuum brazing coating process to improve the high temperature wear resistance and oxidation resistance of single crystal superalloy. Methods of OM, SEM, XRD, EDS, EPMA were employed to investigate the microstructures and compositions of the coatings. Results shows that, the coating consists of γ+γ’, Cr7C3, Cr23C6, Ni3Si and Cr3Si phases. Due to the interfacial interdiffusion, some silicides containing Mo and W are precipitated on the interface, while carbides riched in Ta and Ti with various morphologies are precipitated in the secondary reaction zone of the single crystal superalloy base metal. The hardness of the coating is obviously improved about 3 times, while the distribution is not uniform. The hardness on the interface between coating and substrate is low and the strengthening effect is not obvious because the solid solution strengthening effect is weak, which leads to the hard and the brittle phases have few effects on hardness.