淬火温度对M4粉末高速钢组织和性能的影响

为了研究淬火温度对M4粉末高速钢组织和性能的影响, 利用光学显微镜观察高速钢试样的金相组织, 对淬火组织的晶粒度进行评级, 并对回火组织中碳化物的组成和分布进行统计; 采用洛氏硬度计和材料万能试验机测试试样的硬度和抗弯强度。结果表明: 随淬火温度的升高, M4粉末高速钢淬火后硬度先上升后下降, 在1200 ℃时出现最大值HRC62.9;淬火态试样的晶粒度随淬火温度的升高而降低。经三次回火后M4粉末高速钢硬度值较淬火态均有提高, 且随淬火温度的升高, 先增高后下降, 在淬火温度为1190 ℃时达到最大值HRC66.4。随淬火温度的升高, 回火态试样的抗弯强度逐渐下降, 碳化物聚集长大倾向明显, 尺寸均匀性下降。M4粉末高速钢的最优淬火温度区间为1180~1190 ℃。

Effects of quenching temperature on the microstructure and properties of M4 powder metallurgy high speed steel

To investigated the effects of quenching temperature on the microstructures and properties of M4 powder metallurgy high speed steel (PM HSS), the metallographic structures of the PM HSS samples were observed by optical microscope, the grain sizes of the quenched microstructure were graded, and the composition and distribution of carbide in the tempered microstructure were analyzed. The hardness and bending strengthen of the PM HSS samples were tested by the Rockwell hardness tester and the universal testing machine, respectively. The results show that the hardness of the quenched samples first increases and then decreases with the increase of quenching temperature, reaching a maximum as HRC 62.9 at 1200 ℃. The grain size of the quenched samples declines with the increase of quenching temperature. After the triple tempering, the hardness of the tempered samples is higher than that of the quenched samples, showing the same trend with the increase of quenching temperature. The maximum hardness of the tempered samples reaches HRC 66.4 at the quenching temperature of 1190 ℃. With the increase of quenching temperature, the bending strength of the tempered samples gradually decreases, the carbides coarsen markedly, and the uniformity of carbide dimension deteriorates. According to the results, the optimal quenching temperature of M4 powder metallurgy high speed steel is 1180~1190 ℃.