Parametric investigation of air jet erosion behavior of CrB ₂ - and TiC-reinforced high velocity oxy-fuel (HVOF) sprayed WC–12Co coatings

Air jet erosion is a major degradation mechanism affecting metallic components operating under particle-laden environments. In the present study, a WC–12Co coating reinforced with 5 wt-% CrB ₂ and 5 wt-% TiC was deposited on SS304 stainless steel using the high velocity oxy-fuel (HVOF) spraying process to improve erosion resistance. The developed coating exhibited a dense microstructure with an average thickness of 331 ± 3 μm, low porosity of 1.21 ± 0.09%, and uniform distribution of W, Co, Cr, Ti, and B throughout the coating. Mechanical characterization revealed a significant increase in hardness from 212 ± 7 HV for SS304 to 1232 ± 29 HV for the coated sample. Air jet erosion testing was performed according to ASTM G76 using a Central Composite Design by varying jet velocity, particle size, and impingement angle. The erosion loss of SS304 varied between 10.49 and 29.53 mg, whereas the coated samples exhibited lower erosion values ranging from 6.31 to 25.58 mg. Analysis of variance confirmed that jet velocity was the most influential parameter governing erosion behavior, followed by particle size and impingement angle. The developed quadratic models exhibited high coefficients of determination exceeding 0.99, indicating excellent predictive capability. Post-erosion examination revealed that the coating primarily experienced localized micropitting, particle detachment, and erosion crater formation, while the substrate exhibited severe surface degradation, material extrusion, and surface peeling. The results demonstrate that the incorporation of CrB ₂ and TiC significantly enhances the erosion resistance of WC–12Co coatings, making them suitable for applications subjected to severe particle impingement conditions.