冷处理对超级马氏体不锈钢组织及逆变奥氏体的影响

为研究冷处理对超级马氏体不锈钢的组织性能及逆变奥氏体的影响,通过淬火+回火(A钢)、淬火+冷处理+回火(B钢)以及淬火+深冷处理+回火(C钢)3种工艺进行对比研究。结果表明:实验钢中基体组织为回火马氏体,随回火温度的升高,马氏体板条变细。在相同回火温度下,A钢马氏体板条尺寸较大,B钢次之,C钢尺寸较小、且更平直。实验钢中逆变奥氏体含量随回火温度的升高先增加随后降低,在650℃时达到最大,整个过程中C钢逆变奥氏体含量高于B钢和A钢。实验钢的硬度随回火温度的升高而降低,在650℃时达到最小,随后增大。相同回火温度下,C钢硬度高于B钢,B钢高于A钢。A钢中逆变奥氏体多为块状,尺寸较大,分布较少;B钢次之;C钢中逆变奥氏体多为条状,尺寸较小,且分布均匀。

Influence of cryogenic treatment on the microstructure and reversed austenite in super martensitic stainless steel

The effect of cryogenic treatment on the microstructure, hardness and reversed austenite of super martensitic stainless steel was investigated by comparison of three processes: quenching + tempering (steel A) , quenching + cryogenic treatment + tempering (steel B) and quenching + deep cryogenic treatment + tempering (steel C). The results indicate that in three kinds of steels, the matrixs are martensite and the martensite laths are thinner with increasing tempering temperature. At the same tempering temperature, the martensite laths in steel C are the straightest and the smallest, and the followings are steel B and A. The volume fractions of reversed austenite first increase and then decrease with increasing tempering temperature for the three steels, and reach a maximum value at 650 ??. The reversed austenite content in steel C is more than that in steel A and B over the entire range of tempering temperature. Furthermore, the hardnesses of the steels decrease firstly and reach a minimum value at 650 ??, and then increase with increasing tempering temperature. The hardness of steel C is the highest at the same tempering temperature and the hardness of steel B is between the hardnesses of steel A and C. There is more reversed austenite at Ni- enriched points of the steels. The reversed austenite in steel A is bigger and massive, and the number is smaller. In addition, the reversed austenite in steel C is the smallest with shape of thin strip and distributes more uniformly than that in steel A and B.