循环热处理对1Cr-0.5Mo钢碳化物演变和冲击韧性的影响

Effect of cyclic heat treatment on carbide evolution and impact toughness of 1Cr-0.5Mo steel

采用定量金相法和电解萃取法,结合扫描电镜(SEM)、X射线衍射仪(XRD)、电子探针显微分析仪(EPMA)及低温冲击测试研究1Cr-0.5Mo钢在循环热处理过程中碳化物的演变行为及其对冲击韧性的影响。结果表明:随着循环热处理次数的增加,1Cr-0.5Mo钢珠光体组织中的层片状碳化物逐渐溶解并球化,同时碳化物的类型发生M3C→M23C6的变化;增加循环热处理次数会促进M23C6沿着晶界析出和连接,显著恶化1Cr-0.5Mo钢的冲击韧性,当循环热处理次数达到4次时,M23C6沿着晶界呈链状分布,1Cr-0.5Mo钢的冲击韧性已无法满足使用要求。在循环热处理过程中,1Cr-0.5Mo钢中总体碳化物的平均等效圆直径受层片状碳化物溶解和Ostwald熟化机制的影响表现为先减小后增大的趋势。

The effects of the evolution behavior of carbide on impact toughness of 1Cr-0.5Mo steel during cyclic heat treatment were investigated by quantitative metallographic method and electrolytic extraction method with SEM,XRD,EPMA and low temperature impact test.The results show that with the increasing number of cyclic heat treatment,the lamellar carbides in the pearlite structure dissolve and spheroidize gradually,and the type of carbide also changes:M 3C→M 23 C 6.Increasing the number of cyclic heat treatments promotes the precipitation and connection of M 23 C 6 along the grain boundaries,significantly deteriorates the impact toughness of 1Cr-0.5Mo steel.When the number of cyclic heat treatments reaches 4,the M 23 C 6 grows to chain-like at the grain boundary and the impact toughness of 1Cr-0.5Mo steel can no longer meet the requirements.During the cyclic heat treatment,the average equivalent circle diameter of the overall carbide in 1Cr-0.5Mo steel shows a trend of decrease first and then increase because of the dissolution of lamellar carbides and the Ostwald ripening of carbides.