DD6单晶合金气膜孔薄壁平板高温持久性能

Stress Rupture Behavior of Modeling Specimen with Cooling Holes of Single Crystal Superalloy DD6

在980℃/300 MPa条件下,对带气膜孔与无气膜孔的DD6单晶合金薄壁平板试样进行高温持久试验研究与有限元对比计算。结果表明:在相同名义应力条件下,带孔试样的高温持久寿命比无孔试样的高温持久寿命低,分别为69、90 h,气膜孔的存在破坏了试样的几何连续性,导致气膜孔周围应力集中为主要因素。通过断口宏、微观观察发现,无试样的断裂方式为微孔聚集型断裂,断口上分布着大量方形小平面特征;而带孔试样由于气膜孔改变了试样中的应力分布,在气膜孔附近产生了应力集中,当裂纹扩展至试样边缘,试样被瞬间剪断。基于晶体塑性理论建立了蠕变模型,将其编入ABAQUS的UMAT子程序中对带气膜孔和无气膜孔薄壁平板试样分别进行模拟分析,模拟结果显示与试样的断裂位置及形貌吻合,在工程应用条件下该模型是能用于薄壁平板的高温持久断裂寿命的预测。

Experimental and finite element study on the stress rupture behavior of single crystal superalloy DD6 has been performed with modeling specimens with and without cooling holes at 980 ℃ /300 MPa. The results indicate that the stress rupture life of specimens with cooling holes is 69 h,lower than that without cooling holes（ 90 h） at the same nominal stress conditions. The stress concentration around the cooling holes is the major factor. Scanning electron microscopy analysis on the fracture surface reveals that the specimens without cooling holes fractured in the mode of microvoid coalescence and the fracture surface was made up of small square-shaped facets. As for the specimens with cooling holes,the cracks propagated fast near the holes. Based on the crystal plasticity theory,a creep model was established,and used in the ABAQUS user subroutine（ UMAT）to simulate the plate specimens with and without holes. The results show that the fracture position and fracture pattern are consistent well with finite element numerical analysis. In engineering,the creep model can be used to predict the stress rupture life of thin-walled plate specimens.