火电汽轮机用镍基合金的组织与性能

Microstructure and properties of Ni based alloy used for steam turbine

对火电汽轮机用Ni-6Al-7Ta-4W-4Co-4.6Re-2.8Ru合金进行了固溶和时效热处理,研究了不同温度和外加应力作用下的镍基单晶合金在高温蠕变过程中的蠕变性能和组织演变特征,并分析了其作用机理。结果表明:在外加应力一定条件下,镍基合金的蠕变寿命随着温度的提高而逐渐降低,当温度高于1100℃时表现出了明显的温度敏感性;在温度一定条件下,镍基合金的蠕变寿命随着外加应力的提高而逐渐降低,当外加应力大于156 MPa时表现出了明显的应力敏感性。镍基单晶合金在温度为1075~1125℃、应力为136~176 MPa范围内稳态蠕变阶段的蠕变激活能Q=493.7 k J/mol,应力指数n=4.9;高温蠕变过程中γ'相不断发生扭曲和粗化,在蠕变后期的外加应力作用下,显微裂纹会在γ基体和γ'相界面的显微孔洞处萌生和扩展,并造成镍基合金的蠕变断裂是高温、低应力条件下合金的蠕变断裂机制。

Solid solution and aging were carried out on Ni-Al-Ta-W-Co-4.6Re-2. 8Ru alloy used for steam turbine,the creep behavior and microstructure evolution of Ni based single crystal alloy under different temperatures and applied stress were studied,and its mechanism was analyzed. The test results show that under certain applied stress,the creep life of Ni based alloy decreases with the increase of temperature,and the temperature sensitivity of the Ni based alloy is obvious when the temperature is higher than 1100 ℃. Under certain temperature,the creep life of Ni based alloy decreases gradually with the increase of the applied stress,and the stress sensitivity is obvious when the applied stress is greater than 156 MPa. The creep activation energy（ Q） and stress exponent（ n） of the Ni based single crystal alloy at temperature range of 1075-1125 ℃,stress range of 136-176 MPa are 493. 7 k J / mol and 4. 9 respectively. In the process of high temperature creep,theγ＇ phase is continuously twisted and coarsen,under the effect of external stress at the later stage of creep,Micro cracks initiate and propagate at the interface of the γ matrix and γ＇ phase,and the creep fracture of Ni based alloy is caused,which is the creep rupture mechanism of nickel based alloy at high temperature,low stress conditions.