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利用透射电镜、扫描电镜等试验手段研究了回火温度对2000 MPa和2200 MPa两种强度级别Co-Ni超高强度钢的微观结构、断口形貌与力学性能的影响。结果表明,两种强度级别Co-Ni超高强度钢的强化均与M2C碳化物有关。Co-Ni超高强度钢在400~450℃回火韧性出现谷值,产生的原因与板条边界存在Fe3C、M3C及M2C处于共格状态,使马氏体基体产生强烈静畸变有关,冲击试样断口微观形貌表现为准解理断裂。Co-Ni超高强度钢在480~510℃回火,马氏体板条内析出细小、弥散的M2C,粗大片状Fe3C被细小、弥散的MC取代,使其具有比较好的强韧性配合。
The effects of tempering temperature on the microstructure, fracture morphology and mechanical properties of Co-Ni ultra-high strength steel with two strength grades of 2000 MPa and 2200 MPa were studied by means of TEM and SEM. The results show that the strengthening of the two strength grades of Co-Ni ultra-high strength steel are related to the M2C carbides. Co-Ni ultrahigh strength steel at 400 ~ 450 ℃ tempering toughness appear valley, the reason and the existence of the slab boundary Fe3C, M3C and M2C in a coherent state, the martensitic matrix produced a strong static distortion, the impact of the test Fracture-like microscopic morphology showed quasi-cleavage. Co-Ni ultra-high strength steel tempering at 480-510 ℃, martensitic lath precipitated fine, dispersed M2C, coarse flaky Fe3C by small, dispersed MC replaced, so that it has a better strength and toughness with.