提高Cr-Ni-Mo-Ti马氏体时效不锈钢超低温韧性的固溶处理工艺

Solid solution treatment for improving cryogenic temperature toughness of Cr-Ni-Mo-Ti maraging stainless steel

研究了12Cr-10Ni-Mo-Ti马氏体时效不锈钢在1000℃固溶处理+750℃重复低温固溶处理+不同温度时效处理后的显微组织、室温强度和低温冲击性能,并用XRD分析了不同固溶和时效工艺下的残留奥氏体/逆转变奥氏体含量,对比分析了不同固溶处理工艺下时效响应强度逆转变奥氏体的析出和时效强化规律。结果表明,Cr-Ni-Mo-Ti马氏体时效不锈钢经1000℃固溶处理后再进行750℃低温固溶处理时以α′→γ剪切逆相变形成奥氏体,不仅遗传奥氏体的晶粒形态和尺寸,且形成的奥氏体内高密度缺陷增大马氏体相变抗力,同时显著降低逆转变奥氏体的形成温度,使750℃固溶处理两次时残留16.4%奥氏体,再经460℃峰时效形成了30%以上的残留奥氏体+逆转变奥氏体,液氮温度冲击吸收能量极高,达80 J以上,并且奥氏体的高缺陷密度遗传到马氏体内增强时效强化效应,因此显著改善低温冲击性能的同时并未明显降低抗拉和屈服强度。

Microstructure, room temperature strength and cryogenic temperature toughness of 12 Cr-10 Ni-Mo-Ti maraging stainless steel after solution treatment at 1000 ℃, repeated low temperature solution treatment at 750 ℃ and aging at different temperature were investigated. The amount of retained austenite/reverse transformation austenite under different solution and aging treatment conditions were analyzed by using XRD. The precipitation and aging strengthening rules of reverse transformation austenite in different solution treatment processes were compared and analyzed. The results show that the Cr-Ni-Mo-Ti maraging stainless steel after solution treatment at 1000 ℃ and followed low temperature solution treatment at 750 ℃ forms austenite by α′→γ shear reverse transformation, which not only inherits the grain morphology and size of austenite, but also increases the martensitic transformation resistance and significantly reduces the formation temperature of reverse transformation austenite due to the high density of defects in austenite, resulting in 16.4% retained austenite after double solid solution treatment at 750 ℃, more than 30% retained austenite/reverse transformation austenite is formed after peak value aging at 460 ℃, and the impact absorbed energy at cryogenic temperature is extremely high, reaching above 80 J. Moreover, the high density of defect in austenite is inherited into the martensite, which enhances the aging strengthening effect. Therefore, the low temperature impact property is significantly improved without significantly reducing the tensile strength and yield strength.