超温及应力条件下IC10合金的组织演化及机理

Microstructure evolution and mechanism of IC10 alloy under over-temperature and stress condition

针对燃气涡轮叶片超温运行可能引发的合金劣化问题,对燃气涡轮叶片用IC10合金超温(1070~1250℃)、拉/压应力(30~90 MPa)条件下的微观组演化进行系统分析。结果表明:无应力超温热暴露过程中IC10合金中二次γ′相的退化方式主要包括球化、粗化和回溶,随着热暴露温度的升高及热暴露时间的延长,在γ/γ′相界面能降低的驱动下,二次γ'相形状由花状向圆方状及球状演变。二次γ'相的面积分数随温度的升高及时间的延长逐渐降低。在高于1225℃下热暴露时间超过50 h后,二次γ'相完全回溶。随着温度的升高和时间的延长,二次γ'相尺寸逐渐增加,γ'相粗化符合由元素扩散控制的Lifshitz-Slozov-Wagner理论。在超温有应力热暴露过程中,随着温度的增加,γ'相筏化现象逐渐加剧。拉应力促进γ'相沿垂直于应力轴的方向出现N型筏化,压应力则促进γ'相沿平行于应力轴的方向出现P型筏化。相对于压应力,拉应力状态下γ'相筏化进程更加迅速。根据超温及应力条件下IC10合金的组织演化图谱可对服役后叶片的服役工况进行反向判定。

The microstructure evolution under over-temperature(1070-1250℃)and tensile/compressive stress(30-90 MPa)conditions of IC10 alloy was analyzed to simulate the alloy deterioration process during over-temperature operation of gas turbine blades.The results show that the degeneration of secondaryγ'phase in IC10 alloy during thermal exposure without stress includes spheroidizing,coarsening,and redissolution.As thermal exposure temperature and time increase,the shape of secondaryγ'phase transforms from flower-like to rounded cubic and spherical,driven by the decrease ofγ/γ'phase interface energy.The area fraction of secondaryγ'phase decreases with the increase in temperature and the prolonging of time.The secondaryγ'phase is completely redissolved after thermal exposure at 1225-1250℃for more than 50 h.The size of secondaryγ'phase increases with the increase in temperature and time.The coarsening ofγ'phase conforms to the Lifshitz-Slozov-Wagner theory controlled by diffusion.Under the overtemperature and stress condition,the rafting ofγ'phase gradually intensifies with the increase of temperature.The tensile stress promotes the N-type rafting ofγ'phase perpendicular to the stress axis,while the compressive stress promotes the P-type rafting ofγ'phase parallel to the stress axis.Theγ'phase rafting process is faster under the tensile stress state than under the compressive stress.The microstructure of IC10 alloy under over-temperature and stress conditions can be used to evaluate the service conditions of the blade after service.