【摘要】 以初始组织分别为铸态组织和固溶态组织的第二代镍基单晶高温合金为研究对象,通过进行1300℃、30 MPa、2 h+1300℃、100 MPa、3 h两阶段的热等静压处理,对比热等静压前后显微缺陷及微观组织的变化,并在980℃、250 MPa条件下进行高温持久性能实验,明确了热等静压处理对不同初始组织状态下镍基单晶合金组织状态及持久性能改善的影响机制。结果表明:固溶处理显著促进Re、W、Al、Ta等合金元素的扩散,降低铸态组织共晶面积分数但显著提高显微孔洞平均面积分数及平均尺寸。热等静压处理可以显著降低显微孔洞平均面积分数及平均尺寸且对固溶态组织的作用更为显著,但热等静压对共晶组织的消除作用不如固溶处理明显。固溶态组织经热等静压处理后,显微孔洞面积分数降低至0.005%;共晶组织基本消除;Re、W、Al、Ta等元素枝晶偏析程度显著缓解;其980℃、250 MPa高温持久寿命相比未经热等静压处理的标准热处理态合金提高了40%左右。对固溶态组织进行热等静压处理的工序安排有利于提高显微孔洞闭合作用,促进成分均匀化并显著提高合金高温持久寿命。更多还原

【Abstract】 Due to the excellent high temperature comprehensive performance and cost effective, the second-generation nickel-based single crystal superalloy has been widely used in the high-pressure turbine blades of advanced aero-engines. Microdefects such as micropores and interdendritic eutectic are seriously harmful to the high temperature mechanical properties of nickel-based single crystal superalloys. Hot isostatic pressure(HIP) technology, which has been widely used in powder and casting superalloys, can effectively reduce the micropores, interdendritic eutectic and other structural defects formed in the turbine blades during manufacturing, and improve the service reliability of turbine blades. However,the effect of HIP process on the high temperature stress rupture life of nickel-based single crystal superalloys is still controversial, especially with regard to the initial microstructure state of the nickel-based single crystal superalloys, i.e. the as-cast microstructure state or the as-solid-solution state. In this work, a kind of second-generation nickel-based single crystal superalloy with as-cast state or as-solid-solution state was selected as the research object. Through two-stage heat/booster type heat treatment process, in combination with microdefects quantitative analysis, quantitative characterization of alloying element segregation and high temperature stress rupture tests at 980 ℃ and 250 MPa, the effects of HIP process on the microdefects and high temperature stress rupture life of the used superalloy with different initial microstructures were studied. The results indicated that the solid-solution treatment can significantly promote the diffusion of alloying elements, such as Re, W, Al, and Ta, reduce the area fraction of interdendritic eutectic, but significantly increase the average area fraction and size of micropores in the used alloy with ascast state. While, HIP process can effectively reduce the average area fraction and size of microspores in the used alloy with as-cast state or as-solid-solution state, but cannot eliminate the interdendritic eutectic as remarkable as the solid-solution treatment. By HIP process of the used alloy with as-solid-solution state, the area fraction of micropores is reduced to 0.005%, the eutectic structure is basically eliminated,and the dendrite segregation of Re, W, Al, Ta and other elements is significantly alleviated, resulting in the higher stress ruputure life of the used alloy, about 40% over that of the used alloy with the standard heat treatment state. Performing HIP process on nickel-based single crystal superalloy alloy with as-solidsolution state is of benefit to the high temperature stress rupture life due to the reduction of microdefects and the homogenization of alloying elements, in comparison with performing HIP process directly on the alloy with as-cast sate.更多还原