1990 Volume 76 Issue 6 Pages 956-963
The low BTU coal gasification-complex generation technique was the national project in Japan. In the project, selection of materials for the gas turbine was done. Coal gas which was supplied by gasifier of Coal Mining Research Centre was cleaned up, and then exposure of samples was done under combusting condition close to actual apparatus gas. Specimens of commercial superalloys which were diffusion-coated by aluminium or chromium were evaluated by appearance and by weight change after exposure. Maximum weight loss at 1 000 h was very small to be 11 mg /cm2. But, under certain circumstances, weight loss of base alloys was considerably larger than coated samples. Therefore, the effectiveness of diffusion coating was recognized. The combution gas was found to be oxidative, because of formation of oxide scale. Sulfur was detected in a scale formed in both dry and wet cleaning methods of gas, and alkali metals were also detected in a scale formed in dry-cleaned gas. It was shown that there was influence of sulpheric corrosion on high temperature oxidation. If present samples are evaluated by estimating maximum scaling loss at 10000 h, there will be no problems from a view point of material deterioration.
