High-Temperature Erosive Wear Behavior of High-Velocity Oxy-Fuel Sprayed Cr3C225 (Ni20Cr) Coating on (AISI 316) Austenitic Steel

Abstract

AISI 316 austenitic steel is extensively used in various components of power plants like boilers, boiler tubes and pipes, which suffer severe air jet erosion. Fly ash is a major erodent in that case. Present study is conducted to study the effect of Cr3C225 (Ni20Cr) coating on 316 substrates, when it is exposed to thermal power plant erosive conditions. High-velocity oxy-fuel deposition technique is used for coating. Major constituent of Indian fly ash is alumina, so alumina particles are taken as erodent. Erosion wear behavior is investigated for coated and uncoated conditions using an air jet erosion tester at 100 m/s impact velocity. Three impact angles, i.e., 30 deg, 60 deg, and 90 deg, and four working temperatures, room temperature, 200 °C, 400 °C, and 600 °C, were chosen to identify wear mechanism. Scanning electron microscopy and energy dispersive X-ray spectroscopy (EDX) were utilized to characterize the coated, uncoated, and eroded surface. Erosion behavior is correlated with micro hardness, roughness, and microstructure. Results reveal that the coated surface offers better erosion resistance than the uncoated surface. Substrate exhibits ductile wear behavior as it shows higher wear rate at low angle and decreases on increasing the impact angle, while coating offers good wear characteristics at 30 deg and 90 deg impact angles. An increase in working temperature favors wear rate increment for both coated and uncoated samples. However, coated samples exhibit ductile erosive behavior at high temperatures. Uncoated surfaces have micro-cutting and deformation as major erosive mechanisms. Whereas for coated samples at high temperature, oxide layer formation takes place and erosion takes place due to spalling of the oxides from the coated surface.