固溶处理对航空发动机涡轮机匣力学性能的影响

Effect of Solid Solution Treatment on Mechanical Proper-ties of Aero-Engine Turbine Cases

摘要:

Waspaloy合金广泛应用于航空航天领域，特别是服役环境恶劣的燃气涡轮机。以在役航空发动机涡轮机匣为研究对象，通过现场金相复型技术和实验室验证试验，研究固溶时间和固溶温度对Waspaloy合金低压涡轮（LPT）机匣显微组织和力学性能的影响规律。结果表明，超时固溶（1010 ℃/11 h）对于LPT机匣的显微组织和晶粒度无不利影响。合金对于固溶时间的敏感度较低，随着固溶时间延长（4~20 h），晶粒度未发生变化，晶粒形态基本保持不变，显微组织中孪晶数量逐渐减少，小尺度强化相的占比逐渐增加。合金对于固溶温度的敏感度较高，随着固溶温度由1010 ℃分别升高至1040和1070 ℃，试片的晶粒度级别从7.5级分别降低至6.5级和 3.0级，同时奥氏体晶内的强化相由一次强化相全部转化为二次强化相；另外，γ相晶界处M₂₃C₆碳化物由低温固溶条件下的孤岛状转变为高温固溶条件下的长条状，晶内M₂₃C₆碳化物的数量和尺度也明显增加。合金显微硬度和力学性能主要由合金显微组织中的强化相尺度和晶粒尺度2个因素决定。随着固溶时间延长，显微硬度、抗拉伸强度及屈服强度呈现出逐渐增大的趋势。随着固溶温度升高，合金的显微硬度、抗拉伸强度和屈服强度均呈现出先增加后降低的变化规律。

Abstract:

Waspaloy alloy is widely used in aerospace applications, particularly in gas turbines operating under extreme service conditions. The effects of solid solution duration and temperature on the microstructure and mechanical properties of a Waspaloy low-pressure turbine (LPT) case in in-service aero-engines were investigated via on-site metallographic replication techniques and laboratory verification tests. The results show that excessive solid solution treatment (1010 °C/11 h) has no adverse impact on the microstructure or grain size of the LPT cases. The alloy exhibits low sensitivity to solid solution duration. As the solid solution duration is prolonged from 4 h to 20 h, the grain size remains unchanged, and the grain morphology remains essentially consistent. Only a gradual decrease in the number of twins in the microstructure and a gradual increase in proportion of fine strengthening phases are observed. In contrast, the alloy is highly sensitive to solid solution temperature. When the solid solution temperature increases from 1010 °C to 1040 and 1070 °C, the grain size increases from Grade 7.5 to Grade 6.5 and to grade 3.0, respectively. Simultaneously, the primary strengthening phases within austenite grains are fully replaced by secondary ones. Additionally, M₂₃C₆ carbides at γ phase grain boundaries transition from isolated island-like morphologies (at low temperature) to elongated strip-like morphologies (at high temperature). Simultaneously, both the quantity and size of the intragranular MC carbides significantly increase. The microhardness and mechanical properties of the alloy are predominantly governed by the scale of strengthening phases and grain size. With the prolongation of solid solution duration, the microhardness, tensile strength, and yield strength progressively increase. However, as the solid solution temperature rises, these properties increase first and then decrease.