Corrosion Performance of Newly Developed Stainless Steels for Superheater Tubes of High-Efficiency MSW-to-Power Plants

In order to realize the high-efficiency municipal solid waste(MSW)-to-power generation, an actual plant test of newly developed 20Ni-25Cr stainless steels added 3%Si together with the other conventional superheater tube materials was conducted in an MSW incineration plant in Tokyo. To confirm the effect of Si on high-temperature corrosion, the corrosion performance of developed steels was evaluated at 450 to 500°C for metal surface temperatures with considering the effect of flue gas and steam temperatures, through the detail investigation of various characteristics such as chemistry of the flue gas and ash deposits. The localized corrosion behavior of developed steels was also evaluated. It was proved that adding Si to 20Ni-25Cr stainless steels was also effective in this actual test, and developed steels had a good corrosion resistance rather superior to the conventional 20Ni-25Cr steels, probably due to the combined Cr and Si oxide layer. Moreover, corrosion behavior of welds, which exhibited different modes of corrosion failure, was also evaluated in terms of flue gas and steam temperatures.