On the Microstructural and Tribological Investigations of WC-12Co/NiCrFeSiAlBC HVOF Cermet Coatings: Effects of WC-12Co Fraction

Previous research indicates that WC-12Co contents above 60 wt.% in feedstock powders for cermet coatings impair adhesion and wear resistance. This study characterizes NiCrFeSiAlBC coatings—unreinforced or reinforced with 65 wt.% or 85 wt.% WC-12Co—applied via high-velocity oxy-fuel (HVOF) spraying onto stainless steel substrates under controlled parameters. It quantifies the influence of high carbide volume fractions within the NiCrFeSiAlBC matrix on microstructure and tribomechanical performance. Microstructural analysis revealed uniformly distributed cermet layers featuring dissolved reinforcements and WC hard phase formation, with minimal W2C crystallization. Elevated WC-12Co incorporation promoted densification and reduced porosity. Vickers microhardness tests (HV 0.3) demonstrated increased hardness upon WC-12Co addition, attributable to finer particle sizes, lower porosity, and the presence of WC phases alongside crystallographic refinements. Under dry reciprocating sliding conditions, friction coefficients and wear volumes decreased markedly. Consequently, the coating with 85 wt.% WC exhibited the best mechanical and tribological properties.