Cryogenic Treatment Effect on Microstructure and Tensile Properties of a Low-carbon Martensite Stainless Steel
The effects of different cryogenic treatment and tempering on microstructure and tensile properties of a quenched low-carbon Cr-Co-Ni-Mo high-alloy stainless steel were investigated with SEM,TEM,EBSD and XRD characteristic analyzing and tensile properties testing.The results show that compared with single cryogen-ic treatment and tempering,cryogenic treatment and tempering for two times can promote the transformation of residual austenite to martensite,grain refinement,and carbides precipitation with evener distribution.When the cryogenic treatment with two times keeps for 2 h,reverse transformation of austenite occurs from martensite dur-ing subsequent tempering,bring on the increase of residual austenite content.Increasing the cryogenic time to 4 h,it can lead to a significant reduction of residual austenite content,and an increase of dislocation density and carbide with more uniformly distributed carbides,together with grain refinement.As a result,the strength can be improved obviously,and an excellent balance of strength and ductility can be achieved,having a yield strength of 1 573 MPa,an ultimate strength of 1 979 MPa,and an elongation of 12.7％.
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