含Ru镍基单晶高温合金显微组织和持久性能研究

采用扫描电子显微镜、电子探针和持久性能测试等手段,研究了一种含Ru镍基单晶高温合金的显微组织、偏析行为和持久性能。结果表明,铸态下,Re、W和Ta、Al分别强烈偏析于枝晶干和枝晶间,而Ru及其他元素分布趋于均匀。标准热处理后,合金枝晶干处的γ′相均呈立方状,体积分数和尺寸为63%和0.48μm。合金在980℃/250 MPa、1 100℃/140 MPa和1 120℃/135 MPa条件下的持久寿命分别是364 h、125 h、78 h。长期热处理后,γ′相发生长大粗化,至500 h,发生筏排,但未析出TCP相,表明合金具有较好的组织稳定性;至300 h,合金在1 120℃/135 MPa条件下的持久寿命降至56 h。

Microstructure and Stress-Rupture Property of a Ru-Containing Ni Base Single Crystal Superalloy

The microstructure, segregation behaviour and stress-rupture property of a Ru-containing Ni base single crystal superalloy has been investigated by means of SEM, EPMA and mechanical test. The results showed strong segregate of Re and W in the dendritic regions and Ta and Ti in the interdendritic regions under the as-cast condition, as well as relatively homogeneous distribution for Re and other elements. After standard heat treatment, the γ′ precipitates in the dendritic regions are cuboidal in morphology with a volume fraction of 63% and a mean size of 0.48 μm. The stress-rupture lives are 364 h, 125 h and 78 h under different test conditions of 980 ℃/250 MPa, 1 100 ℃/140 MPa and 1 120 ℃/135 MPa, respectively. Long-term heat treatment at 1 100 ℃ resulted in coarsening of γ′ precipitates, and rafting structure after 500 h annealing, but no TCP phase precipitated, which indicated that the Ru-containing Ni base single crystal superalloy have better the structural stability. The stress-rupture life at 1 120 ℃/135 MPa reduced to 56 h after heat treatment for 300 h.