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

Abstract

<p>Thermally sprayed tungsten carbide (WC) and chromium carbide (Cr<sub>3</sub>C<sub>2</sub>) 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 Cr<sub>3</sub>C<sub>2</sub>-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, Cr<sub>3</sub>C<sub>2</sub>-25NiCr composition is typically selected for high temperature environments, up to 800-900°C. In this study, two distinct Cr<sub>3</sub>C<sub>2</sub>-based compositions of Cr<sub>3</sub>C<sub>2</sub>-50NiCrMoNb and Cr<sub>3</sub>C<sub>2</sub>-37WC-18NiCoCr were selected as interesting alternatives to conventional Cr<sub>3</sub>C<sub>2</sub>-25NiCr. Sliding wear behavior of the coatings sprayed with HVOF and HVAF processes were tested with a ball-on-disk configuration against an Al<sub>2</sub>O<sub>3</sub> ball at room temperature and at 700°C. It was found that both alternative materials had comparable coefficients of friction with the Cr<sub>3</sub>C<sub>2</sub>-25NiCr coatings. The Cr<sub>3</sub>C<sub>2</sub>-37WC-18NiCoCr coatings provided improved wear resistance at room temperature conditions, but at 700°C the wear rate was increased to the level of the Cr<sub>3</sub>C<sub>2</sub>-50NiCrMoNb coatings. Cr<sub>3</sub>C<sub>2</sub>-25NiCr coatings experienced the lowest wear rates at elevated temperatures, which was even lower than at room temperature.</p>