Microstructure and phase transformations of Fe-Ni-Cr mixed powder by laser cladding on Q235 mild steel

The coatings were fabricated by laser cladding with Fe-Ni-Cr mixed powder on Q235 mild steel. The morphology of cross-section, microstructure, phase, microhardness, wear and corrosion resistance of the coating were investigated by optical microscope (OM), scanning electron microscope (SEM), energy dispersive spectrometry (EDS), X-ray diffraction (XRD), Vickers microhardness tester, dry sliding wear testing machine and electrochemical workstation, respectively. Results showed that the metal powder formed good coating without defects such as cracks and pores and the original austenite in substrate transformed into martensite. The phases of coating were solid solution Ni-Cr-Fe and (α-Fe, Ni). The microstrucure of upside, center and bottom of coating were fine equiaxed grains, bulky equiaxed grains and coarse cylindrical crystals, respectively. The cladding coating acquired good wear resistance with the maximum hardness of 578.5 HV0.1and the mean friction coefficient of the substrate is approximately 2 times that of the coating. The corrosion resisting property of cladding is far better than that of substrate by about 9 times.