High-temperature Corrosion Behavior of Heat-resistant Cast Alloys in a Low-grade Fuel Firing Boiler Ash Environment

Abstract

In industrial boilers that use low-grade fuel, high-temperature sulfidation corrosion and vanadium attack have been major issues. High-temperature corrosion tests using actual boiler ash were performed for six heat-resistant cast alloys as candidate materials for burner chips and swirlers. At 850°C, corrosion was not sever, and SCH2 and 50Cr50Ni exhibited particularly good corrosion resistance. However, at 1050°C, corrosion weight loss of 50Cr50Ni, 30Cr70Ni, SCH13, and SCH22 dramatically increased, whereas that of 60Cr40Ni and Ni-less SCH2 was relatively small. Such corrosion mechanisms are discussed on the basis of microstructure observations and the results of EBSD and EDX analyses.