淬火温度对新型NM450抗腐蚀磨损钢组织和性能的影响

采用扫描电镜(SEM)、电子背散射衍射(EBSD)和力学性能检测等方法,研究了淬火温度对NM450抗腐蚀磨损钢组织和力学性能的影响。结果表明,试验钢在840~960 ℃范围内淬火后低温回火,获得了回火板条马氏体组织。当淬火温度为870 ℃ 或低于此温度淬火时,组织中出现了弥散分布的第二相,其Cr含量明显高于基体,当淬火温度升高至900 ℃及以上时,第二相消失,同时奥氏体晶粒也开始明显长大。随着淬火温度的升高,试验钢的强度和硬度整体趋于下降,冲击吸收能量在900 ℃时达到最高。根据取向分布与晶界分布图可以发现,960 ℃淬火时有效晶粒尺寸最大,大角度晶界占比最低,其冲击性能最差。900 ℃淬火时有效晶粒尺寸与840 ℃相近,但其组织结构更加均匀,大角度晶界所占比例升高,这是900 ℃淬火时冲击性能较高的主要原因。

Effect of quenching temperature on microstructure and properties of novel NM450 corrosion-wear resistant steel

Effect of quenching temperature on microstructure and mechanical properties of NM450 corrosion-wear resistant steel was studied by means of scanning electron microscope (SEM), electron backscatter diffraction (EBSD) and mechanical property testing. The results show that the tempered lath martensite microstructure is obtained by quenching at 840-960 ℃ and low temperature tempering. When the quenching temperature is at or lower than 870 ℃, the dispersed second phase appears in the microstructure, and the Cr content is obviously higher than that of the matrix. When the quenching temperature is higher than 900 ℃, the second phase disappears and the austenite grains begin to grow obviously. With the increase of quenching temperature, the strength and hardness of the tested steel tend to decrease, and the impact absorbed energy reaches the highest at 900 ℃. According to the orientation distribution and grain boundary distribution, it can be found that when quenched at 960 ℃, the effective grain size is the largest, the proportion of large angle grain boundary is the lowest and the impact property is the worst. When quenched at 900 ℃, the effective grain size is close to that at 840 ℃, but the microstructure is more uniform, and the proportion of large angle grain boundary increases, which is the main reason for the high impact property when quenched at 900 ℃.