Effect of nano yttria-stabilized zirconia on properties of Ni-20Cr composite coatings

Abstract

In the present work, 5 wt.% and 10 wt.% yttria-stabilized zirconia (YSZ) nanoparticles were reinforced in Ni-20Cr powder and deposited on boiler tube steel using a high-velocity oxy-fuel spraying process. The effect of YSZ reinforcement on microhardness, surface roughness and porosity was investigated. The hardness was the highest for nanocomposite coating reinforced with 10 wt.% YSZ and hardness was found to increase with a decrease in porosity. The coating microstructure and elements were characterized using field emission scanning electron microscopy (FE-SEM) with an energy dispersive spectroscope (EDS). The constituents of the coating were identified using X-ray diffractometer. It was found that the composite coating with 10 wt.% YSZ reinforced nanocomposite coating has the highest microhardness, in the range of 1008-1055 hv. During the coating process, nano YSZ particles were dispersed in the gaps between the micrometric Ni-20Cr particles, providing a better coating matrix than conventional Ni-20Cr. The Ni-20Cr with 10 wt.% of YSZ nanoparticles showed better results in terms of mechanical and microstructural properties during the investigation.