Ni-Cr-W系高温合金组织及高温拉伸变形行为的研究

Microstructure and Tensile Behavior of Ni-Cr-W Base Superalloys at Elevated Temperatures

摘要:

采用光学显微镜、扫描电镜、透射电镜和高温拉伸试验机系统地研究了固溶强化Ni-Cr-W系变形高温合金组织形貌及200~900 ℃范围合金的拉伸变形行为。结果表明，固溶强化Ni-Cr-W系高温合金由奥氏体基体和M6C组成，组织中存在大量的堆垛层错。在650 ℃以下随温度的升高合金的抗拉强度和屈服强度缓慢减小，在650 ℃以上合金的抗拉强度迅速减小，屈服强度基本不变；在650 ℃以下延伸率和断面收缩率变化较小，在650 ℃以上则迅速增大。形变孪晶是导致在400~700 ℃范围内出现锯齿状应力-应变曲线的主要因素。合金断裂方式为韧性韧窝断裂，裂纹主要在γ/M6C结合界面处产生

Abstract:

The microstructure and the tensile deformation behavior between 200 °C and 900 °C of solution strengthened Ni-Cr-W base superalloy were studied by OM, SEM, TEM and a high temperature tensile testing machine. The results show that there are only two phases of γ and M6C in the matrix. Lots of stacking faults are formed in the superalloy microstructure. With the increasing temperature, ultimate tensile strength and yield strength decrease slowly when the temperature is below 650 °C. When the temperature is above 650 °C, ultimate tensile strength decrease rapidly and yield strength almost keep invariable. The elongation and reduction in cross-section of the superalloy change little below 650 °C, but both of them increase rapidly when the temperature is higher than 650 °C. Serration stress-strain curves are induced by mechanical twins mechanism in the temperature range of 400~700 °C. The fracture is of ductile dimple fracture mode. The cracks are initiated mainly in the interface between γ and M6C