High temperature oxidation and erosion-corrosion behaviour of wire arc sprayed Ni-Cr coating on boiler steel

Abstract

In the current investigation, oxidation and erosion corrosion performance of wire arc sprayed Ni-20Cr coating on SA516 and T-22 boiler steel was studied at high temperature. The air oxidation kinetics of wire arc sprayed samples was established on the basis of weight change values for 50 cycles at 900 °C. Each cycle consists of 1 h of heating, followed by 20 min of cooling in air. The erosion corrosion performance of samples was determined by exposing them to the super heater zone of coal fired boiler for 15 cycles at 750°, where each cycle consists of 100 h of heating, followed by 1 h of air cooling. Then, the kinematics of erosion corrosion were established using thickness loss and weight change value of the exposed samples. The distinct characterization techniques (XRD, SEM and EDS) were utilized to examine the oxidized and eroded corroded products. Experimental results reveal that both the coated samples offered more oxidation and erosion corrosion resistance. However, Ni-20Cr coating on SA516 steel perform better than T-22 steel. The Ni-20Cr coated SA516 and T-22 steel reduced the weight gain by 99% and 90% respectively in laboratory environment. Moreover, the Ni-20Cr coating reduced the erosion corrosion rate of SA516 and T-22 steel by 98.04% and 88.23% respectively in terms of thickness loss. The higher resistance against erosion corrosion and oxidation is due to the development of Cr2O3 phase, higher micro hardness and less porosity of the coating.