Microstructural characterization and oxidation, hot corrosion, wear behaviors of APS-sprayed Co–Cr–Ni–W coatings on IN718 alloy

Utilizing atmospheric plasma spraying, Co–Cr–Ni–W coatings were fabricated on Inconel 718 alloy substrate for subsequent investigation of the coatings’ microstructure, high-temperature oxidation behavior, hot corrosion resistance, and friction-wear characteristics, and the damage mechanism was explored. Notably, the coatings exhibited excellent high-temperature stability during oxidation tests, void of delamination or spallation. Over prolonged oxidation periods, the coating surfaces evolved three oxide phases, CoCr₂O₄, Cr₂O₃ and Co₃O₄, as a defense mechanism against oxygen ingress. Internal oxidation commenced near the coating surface and propagated towards the coating/substrate interface. In hot corrosion tests, the coatings developed protective CoCr₂O₄ spinel oxide and Cr₂O₃ layers to combat hot corrosive media and oxygen exposure. With extended hot corrosion durations, the protective oxide on the surface of the coating changed from Cr₂O₃ to CoCr₂O₄. At RT and high temperature wear tests, the COF of the coating decreased with increasing load, and at high temperatures, it exhibited lower wear rates and COF, resulting in superior tribological performance. At RT, the wear mechanisms of the Co–Cr–Ni–W coating primarily included fatigue wear, oxidative wear, and abrasive wear under low loads, as well as oxidative wear and adhesive wear under high loads. At high temperatures, the wear mechanisms of the Co–Cr–Ni–W coating were oxidative wear and adhesive wear.