Performance Analysis of Chromium Carbide Overlay in Coal Nozzle Tip for Utility Boilers

Abstract

Coal Nozzle Tip substrates are laid with chromium carbide alloy overlay to improve the performance life cycle of the component in power boiler. Overlay with hard faced materials exhibits better erosion / wear resistance of the components. Nozzle tips are located in front of the fire ball and gets heated up to 650 ºC due to radiations. The purpose of the investigation is to evaluate the performance of chromium carbide over lay in terms of life cycle. The Chromium rich tubular electrode was used to overlay on plate SA 240 type 309S substrate by Shielded Metal Arc Welding process. Test specimens were prepared for SEM/EDAX, microstructure analysis, hardness and jet erosion test. Surface hardness and jet erosion tests were carried out on hard faced surfaces at elevated temperature 600 ºC and 700 °C. Test results were analyzed and found that the Chromium carbide overlay resulted with low hardness and high erosion at elevated temperature with steeper impact angle.