Hf对抗热腐蚀镍基高温合金微观组织和力学性能的影响

摘要

研究Hf对抗热腐蚀镍基高温合金组织和力学性能的影响;探讨组织演化和力学性能的关系,对于Hf的添加对γ筏形化和/γγ'错配度的影响也进行讨论.结果表明:与无Hf合金相比,含0.4%Hf(质量分数)合金的组织晶界上存在较少的大块状MC碳化物,而细小M23C6碳化物的含量更多,这对蠕变性能有利;Hf的添加有助于使MC碳化物的数量在蠕变过程中保持较高的水平;在长期时效过程中,晶界上碳化物分解为细小离散分布的M23C6碳化物,沿着晶界形成γ'层,无Hf合金的晶界粗化现象更为明显;Hf的添加可以提升合金长期时效后的高温拉伸性能;同时,Hf对提高低应力条件下的蠕变强度作用明显.%The effect of the selective addition of Hf on the mechanical properties and microstructures of experimented nickel superalloy was investigated.The relationship between the microstructure evolution and mechanical properties was studied.Furthermore, the relationship of the appearance of rafting and lattice misfit with regards to Hf content was discussed.The results show that mainly small, coherent, blocky and closely spaced MC and M23C6 carbides precipitate on the grain boundaries in the 0.4％ (mass fraction) Hf-contained alloy, and that relatively larger, incoherent MC carbides precipitate on the grain boundaries in the Hf free alloy.During the long-term thermal exposure, fine discrete M23C6 carbides decompose from primary carbide, inducing γ' layer along the grain boundary, and the coarsening of grain boundary in Hf free alloy is more evident.The selective addition of Hf is beneficial to high temperature tensile strength,and the benefit of Hf content is significant at low stresses.