热处理对一种高硼镍基高温合金组织及力学性能的影响

Effect of Heat Treatment on Microstructure and Mechanical Properties of a High-Boron Ni-Based Superalloy

摘要:

采用SEM、拉伸试验和持久实验等手段探究了热处理对一种高硼Ni₃Al基高温合金组织及力学性能的影响。结果表明，固溶温度由1080 ℃升高至1150 ℃时，枝晶干γ′相的体积分数逐渐降低，形态逐渐由块状向球形转变，γ通道内部析出了细小的三次γ′相。温度由1080 ℃升至1120 ℃时，骨架状一次硼化物部分回溶，颗粒状二次硼化物析出，且随着温度升高，二次硼化物析出倾向增大，温度升至1150 ℃固溶时硼化物完全回溶。经900 ℃×10 h时效后，1080 ℃固溶的合金在800 ℃拉伸时具有900 MPa的极限抗拉强度，在800 ℃/580 MPa具有144.5 h的持久寿命，综合力学性能最优，因此试验合金的最佳热处理工艺为1080 ℃×4 h→空冷+900 ℃×10 h→空冷。

Abstract:

The effect of heat treatment on the microstructure and mechanical properties of a high-boron Ni₃Al-based superalloy was investigated by scanning electron microscope, tensile test and stress rupture test. The results show that when the solid solution temperature increases from 1080 ℃ to 1150 ℃, the volume fraction of γ′ phase in dendrite trunk decreases gradually, the morphology changes from blocky to spherical, and fine tertiary γ′ phases are precipitated inside the γ channel. When the temperature rises from 1080 ℃ to 1120 ℃, the skeleton-like primary borides are partially dissolved, and the granular secondary borides are precipitated. The precipitation tendency of secondary borides is increased with the increase in temperature, and the borides are completely dissolved when the temperature rises to 1150 ℃. After aging at 900 ℃ for 10 h, the alloy solid-solution-treated at 1080 ℃ achieves the ultimate tensile strength of 900 MPa during the tensile test at 800 ℃ and the stress rupture life of 144.5 h under the condition of 580 MPa/800 ℃, exhibiting the best comprehensive mechanical properties. Therefore, the optimal heat treatment process of the test alloy is 1080 ℃×4 h→air cooling+900 ℃×10 h→air cooling.