一次时效温度对单晶高温合金组织和持久性能的影响

Effect of primary aging temperature on microstructure and stress rupture properties of single crystal superalloy

在真空定向凝固炉中采用螺旋选晶法制备了一种镍基单晶高温合金,固溶处理后分别采用1080、1120、1160和1200℃不同的温度进行一次时效,然后在相同工艺下进行二次时效,研究一次时效温度对合金组织和1100℃/140 MPa条件下持久性能的影响。研究表明,随一次时效温度升高,γ'相的尺寸增大,体积分数先增加后减少,在较高温度时效后γ基体通道中有细小的二次γ'相析出,立方化程度先增加后因在1200℃下时效后有部分γ'/γ相界面变为锯齿状而降低。随着一次时效温度提高,合金的持久寿命先增加后降低,在1200℃下时效后持久寿命最低。在1080、1120和1160℃时效后,γ'相在持久过程中形成了完善细密的筏排组织,而在1200℃时效后,γ'相在持久过程中形成了非常不规则的粗化组织。合金在1120℃进行一次时效,合金的组织和持久性能最佳。

Nickel based single crystal with [001] orientation was prepared by screw selecting method in the directionally solidified furnace. The primary aging at 1080,1120,1160 and 1200 ℃ and second aging at the same temperature were subjected after solution heat treatment of the alloy. The effect of primary aging temperature on microstructure and stress rupture properties at 1100 ℃ /140 MPa of the alloy had been investigated. The results show that the size of γ' phase increases and the volume fraction increases first and then decreases afterwards with the increasing of aging temperature. The fine second γ' phase is precipitated in the γ matrix channel after aging at higher temperature. The cubic shape extent of γ' phase increases first and then decreases because the serrated γ' / γ phase surface is formed aging at 1200 ℃. The stress rupture life of the alloy increases first and then decreases afterwards with the increasing of aging temperature. The stress rupture life is the lowest after aging at 1200 ℃. The γ' phase changes into a perfect raft structure after aging at 1080 ℃,1120 ℃and 1160 ℃. However,the γ' phase changes into a very irregular coarse microstructure. The alloy should receive primary aging at 1120℃ to be able to obtain the optimum microstructure and stress rupture property.