High temperature solid particle erosion behaviour of SS 316L and thermal sprayed WC-Cr3C2–Ni coatings

Abstract

The boiler tubes, steam and gas turbines are commonly affected by severe high-temperature erosion wear due to impingement of solid particles entrained in the stream of fluid. The investigation focuses on the applicability of thermal sprayed WC based coatings for turbines and boiler tubes by improving the erosion resistance of the base material. The present work includes high-temperature solid particle erosion behaviour of WC-Cr3C2–Ni coatings deposited by atmospheric plasma spray (APS) and high-velocity oxy-fuel (HVOF) processes. The effects of temperature and impact angle on erosion performance of uncoated and coated specimens were comparatively studied using air-jet erosion tester (ASTM G76). The eroded surface morphology was analysed using a scanning electron microscope (SEM). Uncoated steel exhibit ductile mechanisms; however, both coated specimens follow the mixed mode of material removal under the same operating conditions. Erosion resistance of APS and HVOF coatings is approximately two and three times higher than uncoated specimens at higher temperatures under 30° and 90° impact angles. The HVOF coating offers higher erosion resistance than APS coating due to lower porosity, greater splat adhesion, a lower degree of decarburisation and higher inter-splat sintering at elevated temperatures.