先进超超临界机组用候选材料Alloy 263的组织稳定性

Microstructure Stability of Candidate Material Alloy 263 for Advanced USC Unit

对用于先进超超临界机组锅炉的候选高温合金Alloy 263在固溶处理、沉淀硬化处理和750℃时效3 000 h过程的组织演变行为进行了研究并分析了其组织的稳定性.结果表明：在固溶处理状态下的Alloy 263组织晶粒度为4~5级,较多的一次（Ti、Mo）C弥散分布于γ基体上,且γ′相形核于晶内;沉淀硬化处理主要在晶内共格析出颗粒状γ′相,在晶界析出大量的M23C6;在750℃长期时效条件下,γ′相发生Ostwald熟化,且与基体的错配度增加,M23C6和MC继续析出与长大;在时效1 000 h下基本处于稳定状态,当时效为3 000 h时,有针状η相生成;高温合金Alloy263在750℃下具有良好的组织稳定性.

Microstructure evolution and stability of candidate material alloy 263 for advanced USC（ultra supercritical） unit has been studied respectively during and after the treatment of solution,precipitation and aging at 750 ℃ for 300 h.Results show that at solution treatment state,the grain size of alloy 263 lies in ASTM No.4-5;many primary phases（Ti,Mo）C dispersively precipitate in the γ matrix,and γ′ phase nucleates inside crystal.After precipitation treatment,a lot of M23C6 precipitate on the grain boundary while γ′ phase precipitates coherently in the matrix.As ageing time goes by at 750 ℃,γ′ phases grow according to Ostwald ripening rule;the extent of mismatch between γ′ phase and the matrix increases gradually;the size and quantity of M23C6 and MC increase and tend to be steady at 1 000 h;acicular η phase begins to precipitate in matrix at 3 000 h.Above analysis proves the microstructure of Alloy 263 to be stable at 750 ℃.