Comparing study of high temperature erosion of HVOF sprayed Cr{sub}3C{sub}2-NiCr coating and mild steel for boiler tube

摘要

The significant erosion of the boiler tube at high temperature becomes an important problem for the safe operation of circulating fluidized bed boiler. This paper investigated the erosion behavior of the HVOF sprayed Cr{sub}3C{sub}2-NiCr coating at high temperature comparing with the typical mild steel for boiler tube. Results showed that the erosion rate of the mild steel increased with the increase of temperature. The erosion rate of the mild steel at 800℃ was 4 times that at 300℃ at an erosion angle of 30°. However, the erosion rate of the HVOF sprayed Cr{sub}3C{sub}2-NiCr coating was not influenced by the temperature in the range of 300 to 800℃. It is found that the erosion resistance of HVOF sprayed Cr{sub}3C{sub}2-NiCr coating was more than 3 time higher than that of the mild steel at 700 to 800℃. In addition to the ploughing on the surface of the worn coating, the cracking along splats interfaces in the coating was clearly observed on the cross-sectional microstructure of the coating. The results indicate that the erosion performance of the HVOF sprayed Cr{sub}3C{sub}2-NiCr coating is controlled by the cohesion between splats in the coating and can be further enhanced by improving splat cohesion.