Analysis of the microstructure of Cr–Ni surface layers deposited on Fe3Al by TIG

A series of Cr–Ni alloys were overlaid on a Fe3Al surface by tungsten inert gas arc welding (TIG) technology. The microstructure of the Cr–Ni surface layers were analysed by means of optical metallography, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results indicated that when the appropriate TIG parameters were used and Cr25–Ni13 and Cr25–Ni20 alloys were used for the overlaid materials, the Cr–Ni surface layers were crack-free. The matrix of the surface layer was austenite (A), pro-eutectoid ferrite (PF), acicular ferrite (AF), carbide-free bainite (CFB) and lath martensite (LM), distributed on the austenitic grain boundaries as well as inside the grains. The phase constituents of the Cr25–Ni13 surface layer were γ-Fe, Fe3Al, FeAl, NiAl, an Fe–C compound and an Fe–C–Cr compound. The microhardness of the fusion zone was lower than that of the Fe3Al base metal and Cr25–Ni13 surface layer.