枝晶细化对第三代镍基单晶高温合金显微组织和持久性能的影响

Effect of Dendrite Refinement on Microstructure and Stress Rupture Properties of Third-Generation Nickel-Based Single-Crystal Superalloys

摘要:

采用第三代单晶高温合金WZ30，在不同工艺条件下制备了具有不同枝晶间距的单晶试样，并对其显微组织和持久性能进行 了研究和比较。结果表明，通过改进定向凝固炉加热室与冷却区之间的隔热效果，试样铸件的平均一次枝晶间距从415 μm减小至 251 μm，实现了枝晶和共晶组织的显著细化。同时，枝晶细化后，样品中铸造孔隙率比从2.29%降低至0.21%。此外，枝晶细化后，样品中枝晶干和枝晶间区域的γ′相均发生细化，尺寸分布更加均匀，形状更加规则。经过后续固溶和时效处理后，枝晶细化试样获得了尺寸更小、立方度更高的γ′析出相。在980 ℃/280 MPa条件下，枝晶细化后样品的持久寿命提高了13.8%。

Abstract:

A third-generation single-crystal superalloy WZ30 was used to prepare single-crystal samples with varying dendrite spacings under different processing techniques. The microstructure and stress rupture properties were studied and compared. The results show that, by improving the thermal-insulation effect between heating zone and cooling zone of the directional solidification furnace, the average primary dendrite spacing of the as-cast sample is reduced from 415 μm to 251 μm, leading to a noticeable refinement of dendrite and eutectic structure. At the same time, dendrite refinement can simultaneously decrease the volume ratio of casting porosity from 2.29% to 0.21%. Additionally, the γ′ phase in both the dendritic and inter-dendritic regions undergoes refinement, with a more uniform size distribution and a more regular shape. After the subsequent solid solution and aging treatments, the smaller γ′ precipitates with higher cubic degree are obtained in samples after dendrite refinement, whose service life at 980 °C/ 280 MPa is improved by 13.8%.