Haynes 282 초내열합금의 크리프 강도에 미치는 시효처리의 영향

Abstract

There are presently various problems in coal-fired power plant. The biggest problems are energy shortages and environmental pollution. The main environment of the coal-fired power plant is up to now the USC(Ultra-Super Critical) stage, which is operated at 600°C, and in which used a austenite heat resistant steel as the main turbine material. Generally, as the steam temperature of the high-pressure turbine rises and steam pressure increases, the power generation efficiency of the coal-fired power generation increases and the emission of environmental pollution decrease. Therefore a lot of efforts to rise the steam temperature with the increase of steam pressure. In the next generation coal-fired generation stage of A-USC(Advanced-USC) the steam operating temperature is higher than 700℃. The suitable material for that should be one of Ni-base superalloys. In this study, a superalloy with the same composition as the commercial wrought alloy 282 was casted. The cast alloy 282 was manufactured in 150 kg scale ingot and heat treated in the same of wrought alloy 282. The mechanical property of the casted 282 alloy was compared with that of commercial wrought 282 alloy. The cast alloy 282 had a lower ultimate tensile strength, yeild strength and elongation than the wrought alloy. On the other hand, creep rupture life of both alloys was not significantly different. Furthermore, the aging time of cast alloy 282 were modified. The creep property of the cast alloy 282 with various aging time was investigated. test was carried out with which gave a change in aging time. The creep test was carried out at the temperature of 750℃. The test results showed that the creep rupture life became shorter with longer of aging time. Microstructure of the crept alloys was investigated and test results was analyzed. Creep rupture life was decreased with the increase of aging time which resulted in the coarsening of γ’ precipitation.