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用电镜薄膜技术等研究了6Cr_4Mo_3Ni_2WV基体钢的淬火和回火状态的组织结构,着重观察了硬度一回火温度曲线峰值附近的结构。指出合金的二次硬化主要由V_4C_3和M_2C沉淀产生。回火时沿马氏体内孪晶界和{112}晶面析出的片状渗碳体,低于450℃是稳定的,高于500℃回火是亚稳相,在回火过程中转变为V_4C_3、M_2C和新的细化渗碳体,这对二次硬化也有一定的贡献,但是更主要的是这种转变使合金的冲击韧性α_K值显著提高。在600～650℃回火,亚稳渗碳体的转变区复合变转为M_6C或Cr_7C_3,同时沿原始奥氏体晶界和亚晶界析出连续的等轴M_6C和Cr_7C_3,这一过程又使α_K下降。
The microstructures of quenched and tempered 6Cr_4Mo_3Ni_2WV matrix steels were investigated by means of electron microscopy. The structure of the quenching and tempering of the 6Cr_4Mo_3Ni_2WV matrix steel was studied. The structure near the peak of tempering temperature curve was observed. It is pointed out that the secondary hardening of the alloy is mainly caused by the precipitation of V_4C_3 and M_2C. Tempering along the martensite twins and {112} crystal plane flake cementite precipitation below 450 ℃ is stable, higher than 500 ℃ tempering is a metastable phase in the tempering process into V_4C_3, M_2C and new refined cementite, which also contributed to the secondary hardening, but more importantly, this change made the alloy impact toughness α_K value significantly increased. After tempering at 600-650 ℃, the transformation zone of the metastable cementite changes to M_6C or Cr_7C_3, while the continuous equiaxed M_6C and Cr_7C_3 are precipitated along the original austenite grain boundaries and the subgrain boundaries. α_K decreased.