热处理工艺对叶片用KT5331钢组织和性能的影响

Effect of heat treatment on microstructure and properties of KT5331 steel used for blade

采用SEM、TEM等手段研究了不同热处理工艺下的超超临界机组叶片用KT5331马氏体耐热钢组织和性能。结果表明,KT5331耐热钢随着回火温度的提升,强度稍许下降,冲击吸收能量增加;在1100℃淬火,570℃+690℃两次回火处理后试样的综合性能较好,可以作为最终热处理工艺。组织为板条状回火马氏体,晶界和晶内分布细小的碳化物,并有少量的δ铁素体,冲击断口显示为准解理断裂。增加1150℃+700℃的预处理改善了锻后组织均匀性,但导致原奥氏体晶粒长大,恶化合金的冲击性能。

Microstructure and properties of ultra supercritical unit blade of KT5331 steel after different heat treatment were investigated by means of TEM and SEM. The results show that the strength of the steel declines a little bit and the impact valve increases with temper temperature increasing,the KT5331 steel exhibits excellent integrated properties after quenching at 1100 ℃ and dual-tempering at 570 ℃ ＋690 ℃. The microstructure consists of tempered martensite in lath shape,fine carbides distributed along grain boundaries as well as within the grains,and a small number of δ ferrite,and the appearance of its fracture is quasi-cleavage. The preliminary heat treated of quenching at1150 ℃ and tempering at 700 ℃ can improve the uniformity of the forged microstructure,however,it will result in austenite grain growing and impact toughness reducing.