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通过冲击性能试验、光镜、透射电镜和扫描电镜等方法对超超临界机组用新型奥氏体耐热钢HR3C经650℃时效不同时间后的冲击韧度和显微组织变化进行了研究。结果表明,HR3C钢在650℃时效过程中具有较明显的时效脆化倾向,时效500 h后冲击韧度由时效前的351.7 J/cm2降低到40 J/cm2以下,而后随着时效时间的延长(直至6000 h),冲击韧度基本稳定在20～25 J/cm2;HR3C钢长时时效后的断裂形式主要是以沿晶断裂为主的脆性断裂;时效初期HR3C钢冲击韧度降低的主要原因是由于沿晶析出较多网状M23C6和少量σ沉淀相造成的;时效后期,M23C6出现聚集、球化、长大,但由于σ相的析出量增加,使该钢时效6000 h后的冲击韧度仍保持在较低的水平。
The impact toughness and microstructure of the new type of austenitic heat-resistant steel HR3C after aging at 650 ℃ for different time were studied by impact test, light microscopy, transmission electron microscopy and scanning electron microscopy. The results show that the HR3C steel has obvious aging embrittlement tendency at 650 ℃, the impact toughness decreases from 351.7 J / cm2 before aging to 40 J / cm2 after aging for 500 h, and then decreases with aging time (Up to 6000 h), the impact toughness is basically stable at 20-25 J / cm2. The fracture mode of HR3C steel is mainly composed of intergranular fracture, and the impact toughness of HR3C steel is reduced mainly The reason is that more mesophase M23C6 and a small amount of σ precipitates are precipitated along the grains. At the later stage of aging, M23C6 aggregates, spheroids and grows, but the impact of the steel after aging for 6000 h due to the increased amount of σ phase precipitates Toughness remains at a low level.