Microstructure and properties of ZrO2/Ni3Al-Ni3Al double-layer coating on stainless steel prepared by powder sintering one-step forming process

ZrO _2 /Ni _3 Al-Ni _3 Al double-layer coating on stainless steel was prepared by powder sintering one-step forming process. The surface-interface morphologies, chemical element distribution and phase compositions of the coatings before and after thermal oxidation or hot corrosion were analyzed using scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and X-ray diffractometer (XRD). The microstructure of the coating was Ni _3 Al matrix with dispersed ZrO _2 particles, which was pure and compacted. The Ni _3 Al intermediate layer compactly formed between stainless steel substrate and ZrO _2 /Ni _3 Al composite coating, with good metallurgical bonding interfaces. The ZrO _2 /Ni _3 Al-Ni _3 Al double-layer coating exhibited a relatively high outmost microhardness of about 500 HV, and then gradually decreased from the coating to the substrate. When thermal oxidized or hot corroded at 1050 °C, a mixed oxide layer of NiO, Al _2 O _3 and NiAl _2 O _4 formed on the coating surface, which effectively acted as a diffusion barrier for oxygen and corrosive substances, and thus demonstrated the good protective effect of ZrO _2 /Ni _3 Al coating.