Corrosion–Cavitation Erosion Improvement of Marine Steel by High-Velocity Oxy-fuel-Sprayed Vanadium Carbide Coatings and Polytetrafluorethylene Topcoat

Abstract

This study looks into ways to improve cavitation erosion and corrosion resistance of SS316 steel material using HVOF-sprayed vanadium carbide (VC) and polytetrafluorethylene (PTFE) topcoat. Optimal conditions were evaluated using the response surface methodology, resulting in a considerable reduction in mass loss. Material-specific cavitation responses revealed that HVOF-sprayed VC had greater resistance, which may be attributable to its improved hardness (1323 HV). The reactions of PTFE-sprayed samples varied, demonstrating the complex interaction between PTFE characteristics and jet velocities. Scanning electron microscopy images confirmed the efficiency of HVOF-sprayed VC and PTFE coatings as corrosive element barriers. In a cyclic corrosion test, VC coating created a dense, stable oxide layer; however, PTFE showed great corrosion resistance and impermeability even after seven cycles. After coating the SS316 substrate with VC and PTFE, percentage improvements of cavitation resistance compared to the SS316 were observed to be 28.8 and 55.3%, while the percentage improvement of corrosion resistance was observed to be 68 and 79.7%, respectively, for VC and PTFE. Furthermore, HVOF-sprayed VC and PTFE coatings, along with laser texturing, converted surfaces into superhydrophobic ones (water contact angle: WCA > 158°). Comprehensive mechanical evaluations revealed microhardness, porosity, surface roughness, and bond strength, revealing VC robust resistance to indentation and created strong bond strength with the substrate as (72.8 MPa). These findings suggest methods and coatings for improving material resistance in cavitation-prone and corrosive environments.