Effect of Deposition Defects on the Wear and Corrosion Resistance Behavior of HVOF-Sprayed 304 Stainless Steel Coatings

In this study, 304 stainless steel (304SS) coatings were deposited by high-velocity oxygen-fuel (HVOF) spraying at varying oxygen-fuel (OF) ratios and spraying distances. The effects of deposition defects and solidification phase structures on dry sliding wear and electrochemical corrosion were systematically investigated. The results indicate that the spraying parameters altered particle melting, spreading, solidification, and oxidation, thereby governing porosity, oxide content, and phase composition of the coatings. Consequently, the OF-4.7/D-250 coating exhibited the densest structure, with 1.8 vol. % porosity, 2.1 wt. % oxygen, and approximately 10 wt. % martensite, achieving the lowest wear rate of (1.60 ± 0.01) × 10−5 mm3·N−1·m−1 and corrosion current density (1.29 ± 0.09) × 10−6 A·cm−2. Wear resistance is collectively influenced by porosity, oxides, and phase composition, whereas corrosion resistance is mainly affected by porosity, followed by oxides. Austenite remained dominant in all coatings (≥77 wt. %), so the influence of phase composition on corrosion was comparatively limited. The deposition defects dominate the variation in wear and corrosion resistance of the HVOF-sprayed 304SS coatings.