C含量对K465镍基高温合金组织及高温持久性能的影响

Influence of C Contents on Microstructure and High Temperature Stress Rupture Properties of Polycrystalline Nickel-based Superalloy

通过对不同C含量的K465合金进行显微组织观察、DSC分析和力学性能测试,研究了C含量对K465镍基高温合金组织演变及高温持久性能的影响。结果表明,合金凝固期间碳化物的析出温度和数量受C含量影响较大,且随C含量增加而提高,共晶转变温度及数量随着C含量增加而降低。合金中碳化物的数量随着C含量的提高逐渐下降,而合金中共晶组织和γ’相的数量随着C含量的增加逐渐减少。合金经过固溶热处理后MC碳化物退化分解成M6C碳化物。合金在975℃/225 MPa持久变形期间的断裂机制为裂纹在共晶和晶界处萌生并沿晶界扩展。随着C含量的增加,组织中共晶数量减小,晶界强化相M6C数量增加,合金的持久性能得到一定改善;但随着C含量增加到0.2wt%,合金中γ’相减少,导致合金的持久性能明显下降。

The influence of C contents on the microstructure evolution and stress rupture properties of K465 alloy were studied by investigating microstructure, DSC analysis and mechanical tests. The results show that the precipitation temperature and the quantity of the carbides are mainly affected by the content of C, which are both increased with the increase of C in the alloy. The transition temperature of eutectic and the quantity of eutectic decreases with the increase of C content. With the increase of C content, the quantity of carbides increases, while the quantity of eutectic and γ’ phase decreases. The fracture mechanism of the alloy during stress rupture deformation at 975 ℃/225 MPa is initiation of cracks from the grain boundary and the eutectic, and the cracks propagate along the grain boundary. As the increase of C content, the quantity of eutectic decreases, and the quantity of MC increases, which results in the improvement of the stress rupture time. However,the decrease of the quantity of γ’ phase with the C content increasing to 0.2 wt% would deteriorate the stress rupture life.