Slurry Erosion Resistance Through HP-HVOF-Sprayed WC–10Co–4Cr Coatings with Rare Earth Elements and Response Surface Methodology Analysis

This study aimed to enhance the performance of SS410 steel against slurry erosion through high-pressure-high-velocity oxy fuel (HP-HVOF) spraying of coatings incorporating rare earth elements. Four types of ceramic coatings were developed: pure WC–10Co–4Cr (Sample A), WC–10Co–4Cr with 0.9% La₂O₃ (Sample B), WC–10Co–4Cr with 0.9% CeO₂ (Sample C), and WC–10Co–4Cr with 0.9% Er₂O₃ (Sample D). Cross-sectional SEM analysis revealed dense coatings with average thicknesses of 360 µm, 346 µm, 346 µm, and 327 µm, respectively. The mechanical properties improved with the addition of rare earth elements, resulting in increased microhardness (996–1382 HV) and bond strength (71–78 MPa). Porosity decreased, particularly in Sample D (0.89%). Slurry erosion tests indicated that Sample D exhibited the lowest mass loss across various conditions, suggesting superior erosion resistance. SEM images post-erosion showed varying degrees of surface degradation, with Sample D displaying fewer cracks and pores but signs of brittle failure. The response surface methodology demonstrated that velocity, impingement angle, and slurry concentration significantly impacted mass loss. ANOVA results confirmed the significance of these parameters, with p values below 0.05 and non-significant lack-of-fit statistics. The high desirability range achieved (0.91–0.99) demonstrates the effectiveness of the model in predicting process outcomes and highlights the capability of the desirability function method to optimize multiple responses effectively. These findings highlight the potential of rare earth elements in enhancing the durability of HP-HVOF-sprayed coatings for hydromachinery applications.