Surface Modification of TC4 by High Velocity Oxy-Fuel

High-velocity oxy-fuel tungsten carbide coatings demonstrate superior microhardness and neutral salt spray corrosion resistance relative to electroplated hard chromium. Their inherent toughness and high bond strength with substrates establish this technology as an ideal replacement for conventional hard chromium plating. This study employed high-velocity oxy-fuel spraying to deposit WC-10Co-4Cr coatings on TC4 titanium alloy, significantly enhancing surface properties with substantially improved corrosion resistance, wear resistance, and microhardness. A weld-like interfacial morphology with distinct solid-solution lines was observed, bordered predominantly by dendritic and equiaxed crystals. Microhardness progressively increased from the TC4 substrate across the interface to the WC-rich coating zone, reaching a maximum value of 1285 HV. This hardness gradient is attributed to synergistic effects of solid-solution strengthening by W/Co interdiffusion, increased volume fraction of hardening phases, and grain coarsening.