Slurry Erosion Behavior of Thermally Sprayed Nano YSZ Reinforced WC-10Co-4Cr Ceramic Nanocomposite Coatings

The presence of nanoparticles in the conventional coatings improves their strength by increasing the microhardness and reducing the porosity. The nanocomposite coatings play a significant role in increasing the erosion resistance. The purpose of this study is to observe the erosion behavior of nano yttria stabilized zirconia (Y2O3/ZrO2; YSZ) reinforced WC-10Co-4Cr ceramic nanocomposite coatings. The WC-10Co-4Cr conventional coating powder, and 95% and 90% of WC-10Co-4Cr reinforced with 5% and 10% of nano YSZ powders, coated on CA6NM steel using a high-velocity oxygen fuel (HVOF) spraying process. The Taguchi method using an L-9 orthogonal array was applied for experimental design. Erosion test rig was used to perform erosion experiments at various levels of selected parameters. The results of erosion experiments and analysis of variance (ANOVA) for the conventional and nanocomposite coatings revealed that impact velocity performs a significant role in the material loss, followed by slurry concentration, average particle size, and impingement angle. Scanning electron microscopy (SEM) analysis of eroded samples revealed that cracks, protuberances, deep craters, spalling, ploughing, micropores, microcutting, lip formation, chip formation and microcracks are mainly responsible for the erosion of substrate material and different types of coatings. Inclusion of nanoparticles of YSZ into the WC-10Co-4Cr microparticles increased the microhardness and decreased the porosity of the nanocomposite coatings. Thus, the silt particles cannot penetrate more deeply into the metal surface and provided high resistance to erosion. It was observed that 95% (WC-10Co-4Cr) + 5% YSZ and 90% (WC-10Co-4Cr) + 10% YSZ ceramic nanocomposite coatings exhibits higher resistance to erosion in comparison with WC-10Co-4Cr coating and substrate material, due to better mechanical properties.