热疲劳对B/M复相H13钢组织及力学性能的影响

为提高其热疲劳性能,对H13钢进行了贝氏体-马氏体(B/M)复相热处理,使其得到了由回火索氏体和贝氏体组成的复相组织。利用OM、SEM、TEM、洛氏硬度计、万能拉伸试验机等设备研究了热疲劳对B/M复相H13钢微观组织、碳化物及力学性能的影响。结果表明:较传统H13钢硬度随疲劳次数增加而迅速降低的现象,B/M复相H13钢的硬度随疲劳次数的增加呈先下降后上升再下降的趋势。拉伸试验表明,较传统H13钢,B/M复相H13钢的强塑性配合更加优异,且在热疲劳后,其断面收缩率反而有所增大。通过显微组织观察发现力学性能变化的主要原因是B/M复相H13钢在热疲劳过程中存在贝氏体板条合并及碳化物析出并长大粗化的行为。

Effect of thermal fatigue on microstructure and mechanical properties of B/M multiphase H13 steel

In order to improve its thermal fatigue property, H13 steel was B/M multiphase heat treated to obtain a tempered sorbite+bainite multiphase microstructure. The effect of thermal fatigue on the microstructure, carbide and mechanical properties of the B/M multiphase H13 steel was investigated by means of OM, SEM, TEM, Rockwell hardness tester and universal tensile testing machine. The results show that contrast to the phenomenon of rapid decrease of hardness with the increase of fatigue circle for the traditional H13 steel, the hardness of B/M multiphase H13 steel decreases first and then rises and then decreases with the increase of fatigue circle. The tensile experiments show that the strength-plasticity cooperating of the B/M multiphase H13 steel is better than that of the traditional H13 steel, and its percentage reduction of area increases after the thermal fatigue. It is found from microscopic observation that the main reason for the change in mechanical properties is the bainite lath merging and carbide precipitation and coarsening in the B/M multiphase H13 steel during thermal fatigue.