Sliding wear behaviour of HVOF and HVAF sprayed Cr3C2-based coatings

Thermally sprayed tungsten carbide (WC) and chromium carbide (Cr3C2) based hard metal coatings are commonly applied on component surfaces as corrosion and wear resistant layers. Typically, WC-Co/Ni with optional Cr addition and Cr3C2-25NiCr powders are sprayed with high velocity oxy-fuel (HVOF) or high velocity air-fuel (HVAF) processes. Due to the poor oxidation resistance of the WC particles, Cr3C2-25NiCr composition is typically selected for high temperature environments, up to 800-900 degrees C. In this study, two distinct Cr3C2-based compositions of Cr3C2-5ONiCrMoNb and Cr3C2-37WC-18NiCoCr were selected as interesting alternatives to conventional Cr3C2-25NiCr. Sliding wear behavior of the coatings sprayed with HVOF and HVAF processes were tested with a ball-on-disk configuration against an Al2O3 ball at room temperature and at 700 degrees C. It was found that both alternative materials had comparable coefficients of friction with the Cr3C2-25NiCr coatings. The Cr3C2-37WC-18NiCoCr coatings provided improved wear resistance at room temperature conditions, but at 700 degrees C the wear rate was increased to the level of the Cr3C2-50NiCrMoNb coatings. Cr3C2-25NiCr coatings experienced the lowest wear rates at elevated temperatures, which was even lower than at room temperature.