K465合金蠕变空洞的愈合机理及模型研究

发布时间：2018-04-19 05:23

本文选题：镍基高温合金 + 热等静压　；参考：《安徽工业大学》2017年硕士论文

【摘要】：镍基高温合金广泛应用于制造航空发动机热端部件,通常在高温、高压、复杂应力以及燃气腐蚀等苛刻服役条件下运行。在长期服役过程中,镍基高温合金会不可避免地产生显微组织退化甚至出现蠕变空洞,降低材料的力学性能和使用寿命。热等静压(HIP)恢复技术被证明可以有效治愈镍基高温合金的服役损伤,使退化的显微组织重新恢复以及愈合蠕变空洞。但是,最佳热等静压工艺参数的确定通常依赖于大量的实验数据和工程经验,而蠕变空洞在热等静压作用下的愈合机理及动力学模型研究可以为热等静压工艺参数的优化选取提供依据。本文采用光学显微镜和扫描电镜对K465镍基高温合金的原始铸态、蠕变损伤态和HIP处理状态的显微组织进行了定量分析,研究了热等静压处理前后K465合金微观组织演化行为,并采用有限元方法(FEM)分析了含蠕变空洞的K465高温合金在热等静压作用下的应力场分布情况,以研究镍基高温合金蠕变空洞的愈合行为。结果表明,当HIP温度不足以完全溶解一次γ’粒子但HIP处理能产生有效愈合时,在蠕变空洞附近会形成同心γ’筏排结构。外加等静压力的作用改变了蠕变空洞附近γ基体和γ’粒子的应力场,具有明显的各向异性分布特性,导致溶质原子发生定向扩散,进而形成同心γ’筏化结构。考虑晶界扩散和基体蠕变的共同作用,提出了热等静压作用下的蠕变空洞愈合动力学模型,并对模型参数进行数值分析,定量分析热等静压温度和等静压力对蠕变空洞愈合时间的影响,构造了蠕变空洞的HIP愈合图。结果表明,愈合时间均随温度和压力的增加而急剧降低;相比于HIP压力,愈合时间对HIP温度的敏感性更大;对于晶界大尺寸空洞甚至晶界完全分离,它们所需的愈合时间比小尺寸空洞要长得多;等静压力在150MP以上继续增加,对空洞愈合效果并无太多改善。
[Abstract]:Nickel-based superalloys are widely used in the manufacture of hot end components of aero-engines, which usually operate under harsh service conditions such as high temperature, high pressure, complex stress and gas corrosion.In the long service process, the microstructure of Ni-base superalloy will inevitably degenerate and even creep cavity will appear, which will reduce the mechanical properties and service life of the material.The hot isostatic pressure (HIP) recovery technique has been proved to be effective in curing the service damage of nickel-based superalloys, restoring the degraded microstructure and healing the creep voids.However, the determination of the optimum process parameters of hot isostatic pressing usually depends on a large number of experimental data and engineering experience.The study on the healing mechanism and dynamic model of creep cavity under the action of hot isostatic pressure can provide the basis for the optimization of process parameters of hot isostatic pressing.In this paper, the microstructure of K465 nickel-based superalloy was quantitatively analyzed by optical microscope and scanning electron microscope. The microstructure evolution behavior of K465 alloy before and after hot isostatic pressing was studied.The stress field distribution of K465 superalloy with creep voids under hot isostatic pressure was analyzed by means of finite element method (FEMM) to study the healing behavior of creep voids in nickel-based superalloys.The results show that the concentric 纬 'raft structure will be formed near the creep cavity when the HIP temperature is not enough to completely dissolve the single 纬' particle but the HIP treatment can produce effective healing.The stress field of 纬 matrix and 纬 'particles near creep voids is changed by the action of isostatic pressure, which has obvious anisotropic distribution and leads to directional diffusion of solute atoms and the formation of concentric 纬' rafting structure.Considering the interaction of grain boundary diffusion and matrix creep, a dynamic model of creep cavity healing under hot isostatic pressure is proposed, and the parameters of the model are analyzed numerically.The effects of thermal isostatic pressure temperature and isostatic pressure on the healing time of creep voids are quantitatively analyzed and the HIP healing diagram of creep voids is constructed.The results show that the healing time decreases sharply with the increase of temperature and pressure, and the healing time is more sensitive to HIP temperature than that of HIP pressure.Their healing time is much longer than that of small size voids, and the effect of cavity healing is not improved much if the static pressure increases over 150MP.
【学位授予单位】：安徽工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG132.3

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