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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。
The microstructure and properties of KT5331 martensite heat-resistant steel for blade of ultra-supercritical units under different heat treatments were studied by means of SEM and TEM. The results show that the strength of KT5331 heat-resistant steel decreases slightly with the increase of tempering temperature, and the energy of impact absorption increases. After being tempered at 1100 ℃ and twice tempering at 570 ℃ and 690 ℃, the comprehensive performance of the sample is good, Heat treatment process. Tissue lath tempered martensite, grain boundaries and intragranular distribution of small carbides, and a small amount of δ ferrite, impact fracture shows quasi-cleavage fracture. Increasing the pretreatment at 1150 ℃ + 700 ℃ improved the homogeneity of the forged alloy, but resulted in the growth of the original austenite grains and worsened the impact properties of the alloy.