Comparative Study on the Microstructure and Properties of 304 Stainless Steel Coatings Prepared by High-Velocity Oxygen Fuel Spraying and Air Plasma Spraying

The 304 stainless steel coatings were applied to a 6061-T6 aluminum alloy substrate using high-velocity oxygen fuel spraying (HVOF) and air plasma spraying (APS) techniques. The objective of this study was to investigate the microstructure, hardness, tribological, and corrosion properties of the coatings produced by these two different processes. The findings revealed a clear relationship between the molten state of particles and the porosity, oxygen content, and microstructure of the stainless steel coatings. It was observed that the HVOF coating had higher quantities of austenite and martensitic, while the APS coating exhibited an increased presence of ferrite. These distinctions were directly responsible for the enhanced hardness and improved wear resistance observed in the HVOF coating. More specifically, the HVOF coating demonstrated a twofold increase in hardness (493.2 Hv0.1) compared to the APS coating. Its wear resistance was also significantly improved, with a sevenfold increase (0.36 x 10-4 mm3 N-1 m-1). Electrochemical tests were performed in a 3.5 wt.% aCl solution to assess the corrosion behavior of the coatings. The results clearly indicated that the HVOF coating provided superior corrosion protection compared to the APS coating.