热处理对马氏体不锈钢显微组织和性能影响

Effects of Heat Treatment on Microstructure and Mechanical Properties of Martensitic Stainless Steel

借助强度和硬度测量手段以及显微组织观察及EDS能谱分析,研究了奥氏体化温度和时间、回火温度对一种实验室冶炼的马氏体不锈钢的微观组织和力学性能的影响。实验结果表明:奥氏体化温度可以显著影响材料的力学性能,当奥氏体化工艺为1050℃-60 min时,材料的硬度最大(49 HRC),抗拉强度最高(1800 MPa)。在回火温度为400~500℃的范围内,回火温度的升高导致了M_7C_3相的沉淀和二次硬化,使材料的硬度和抗拉强度轻微升高;当回火温度进一步升高至700℃时,M_7C_3碳化物发生粗化并部分地转变为M_(23)C_6碳化物,材料的硬度和抗拉强度明显降低。试样在200℃和700℃回火后的拉伸断口表现出混合断裂机理(脆性和韧性),而在500℃表现为韧性特征。该材料最佳的热处理工艺为1050℃-60 min奥氏体化处理+500℃-60min回火处理。

The influence of austenitizing temperature, austenitizing time and tempering temperature on microstructure and mechanical properties of a martensitic stainless steel prepared in laboratory was investigated by means of strength and hardness measurement, microstructure observation and EDS energy spectrum analysis. The experimental results show that the austenitizing temperature can significantly affect the mechanical properties of the material. When the austenite temperature is1050 ℃-60 min, the material owns the best hardness（49 HRC） and tensile strength（1800 MPa）. When the tempering temperature is in the range of 400-500 ℃, the hardness and tensile strength increase slightly with the tempering temperature increases for the cause of the precipitation of M7C3 phase and secondary hardening. When the tempering temperature increases furtherly to 700 ℃, M7C3 carbide becomes coarse and partially converte to M（23）C6 carbide, and the hardness and tensile strength decrease obviously. The tensile fracture surfaces of the specimens tempered at 200 and 700 ℃ exhibit mixed fracture mechanisms（brittleness and toughness）, while they exhibit ductile characteristics at 500 ℃. The best heat treatment process of the material is 1050 ℃-60 min austenitizing treatment, and 500 ℃-60 min tempering treatment.