W元素对M50钢中碳化物及力学性能的影响

Effect of W on Carbides and Mechanical Properties in M50 Steel

为减小碳化物尺寸,提高M50钢的力学性能,制备了一种含W元素的改进M50钢(M50+W钢),研究了W元素对M50钢微观组织和力学性能的影响。结果表明:相同温度下,M50+W钢的硬度始终高于M50钢,M50+W钢在室温和400℃时的屈服强度均有所增大;添加W元素后,M50钢中一次碳化物长轴平均尺寸由3.39μm减小至1.61μm,形状从长棒变为椭球体,二次碳化物平均直径由343 nm减小至162 nm。根据碳化物形核与长大机制,并通过Thermo-Calc软件计算发现,回火温度下,W元素的添加降低了析出碳化物与基体之间的界面能,增加了碳化物的析出驱动力,提高了形核率,从而减小了碳化物尺寸,提高了M50钢的高温硬度和强度。

In order to reduce the size of carbides and improve the mechanical properties of M50 steel,a modified M50 steel containing W(M50+W steel)is prepared.The effects of W on microstructure and mechanical properties of M50 steel are studied.The results show that the hardness of M50+W steel is always higher than that of M50 steel under same temperature,and the yield strength of M50+W steel increases under both room temperature and high temperature of 400℃;after W is added,the average size of long axis of primary carbides in M50 steel decreases from 3.39μm to 1.61μm,and the shape changes from long rod to ellipsoid,the average diameter of secondary carbides decreases from 343 nm to 162 nm.According to nucleation and growth mechanisms of carbides,and calculated by Thermo-Calc software,it is found that under tempering temperature,the addition of W reduces the interfacial energy between precipitated carbides and matrix,increases the driving force for precipitation of carbides,improves the nucleation rate,thus reducing the size of carbides and improving the high temperature hardness and strength of M50 steel.