热处理工艺对18%Cr马氏体不锈钢组织与力学性能的影响

Effect of heat treatment on the structure and mechanical properties of 18%Cr martensitic stainless steel

以羰基Fe粉以及Cr_3C_2,VC,Mo_2C等碳化物粉末为原料,制备Cr含量(质量分数,下同)为18%的粉末冶金马氏体不锈钢。将不锈钢分别在1 050℃和1 150℃下淬火,然后于200~590℃下进行回火处理,研究热处理工艺对不锈钢组织与力学性能的影响。结果表明:粉末冶金18%Cr马氏体不锈钢的基体中存在M_7C_3型以及MC型碳化物,随回火温度升高,碳化物数量增多并且碳化物形态由原来的部分连续状向孤立、块状转变。1 150℃温度下淬火的不锈钢,其硬度较高,HRC最高达63.9,在较低温度下(200℃)回火时,抗弯强度为2 002 MPa,而在530℃温度下回火后,抗弯强度大幅升高至3 093 MPa。1 150℃淬火的不锈钢,其冲击韧性较低,随回火温度升高而升高。热处理后的不锈钢断裂形式均为准解理断裂。

The powder metallurgy martensitic stainless steel with Cr content （mass fraction, the same below） of 18% was prepared by using carbonyl iron powder, Cr3C2, VC and MOEC as raw materials. The stainless steel was quenched at 1 050℃ and 1 150 ℃ respectively, and tempered at the temperature varying between 200 and 590 ℃, to study the effects of heat treatment on the microstructure and mechanical properties of stainless steel. The results show that： M7C3 and MC carbides exist in the matrix of stainless steel. With increasing tempering temperature, the quantity of carbides increase and the morphology changes from original continuous shaped carbide to the isolated block shaped. After quenching at 1 150℃, the hardness is higher, up to 63.9 HRC. When tempering at lower temperature （200 ℃）, the bending strength of specimens quenched at 1 150 ℃ is 2002 MPa. While tempering at 530 ℃, the bending strength increases sharply to 3 093 MPa. The impact toughness of the stainless steel quenched at 1 150℃ is lower, it increases with increasing the tempering temperature. The fracture mode of all of the samples is quasi-cleavage fracture.