Recoating and Refurbishment of Single crystal Ni- Based Superalloys for Advanced Gas Turbines

先进燃气轮机用单晶镍基高温合金的重涂和翻新

基本信息

批准号：
10650078
负责人：
OKAZAKI Masakazu
金额：
$ 2.24万
依托单位：
The University of Tokyo (1999)Nagaoka University of Technology (1998)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

项目摘要

This work has been conducted to make clear the formation of the abnormal microstructure, or cellular transformation, resulting from the local plastic deformation in single crystal Ni-base superalloys, CMSX-2 and CMSX-4, in order to get fundamental understanding to establish the refurbishment technology for advanced gas turbine components. During the study special attention was paid to get understandings on the nucleation and growth behavior from viewpoints of crystallography and thermo dynamics. The relationship between the transformation and the actual failure damages was also explored. Furthermore, the effect of the local cellular transformation on high temperature fatigue strength was investigated.The conclusions obtained are summarized as follows :(1) When CMSX-2 and CMSX-4 were subjected to damages associated with local plastic deformation, followed by the re-heat treatments, the cellular transformation associated with γ/γ' microstructure coarsened in lamellar or equiaxed array wa … More s originated. This was not a special phenomenon, but it was actually reproduced in the material subjected to fatigue and thermo-mechanical fatigue damages.(2) The transformation was originated and developed with high anisotropy, being influenced by the following many factors : i.e., the strain field by the local plastic deformation, the crystallographic orientation, the re-heat treatment temperature and time, and the microsegregation in the material. The γ'-solvus in the reheating process drastically accelerated the local recrystallization.(3) The shearing of γ' precipitates in the straining process may play an intrinsic role in the cellular transformation : when the {111}<110> systems were activated, the formation was significant. When the {100}<110> slip systems were activated such as in creep failure at higher temperature, on the other hand, it was negligible.(4) The growth of the transformation was successfully represented by the Johnson-Mehl type equation. The growth of the transformation must be controlled by diffusion process of A1 and Ni, where activation energy was determined by about 36 kcal/mol.(5) The small fatigue crack propagation rate was remarkably enhanced at the transformed region. Less

这项工作的目的是弄清楚单晶镍基高温合金 CMSX-2 和 CMSX-4 中局部塑性变形引起的异常微观结构或胞状转变的形成，以便从根本上了解建立在研究过程中，特别关注从晶体学和热力学的角度了解成核和生长行为，并探讨了转变与实际失效损坏之间的关系。此外，还研究了局部胞状转变对高温疲劳强度的影响。得到的结论概括如下：(1)当CMSX-2和CMSX-4遭受局部塑性变形损伤时，随后进行了高温疲劳强度分析。 -热处理时，与片状或等轴阵列中粗化的 γ/γ' 微观结构相关的细胞转变起源于这并不是一种特殊现象，但它实际上在遭受疲劳和热机械疲劳的材料中重现。 (2)相变的产生和发展具有高度的各向异性，受局部塑性变形产生的应变场、晶体取向、再热处理温度和时间、微观偏析等多种因素的影响。再加热过程中的γ'-固溶线迅速加速了局部再结晶。(3)应变过程中γ'析出物的剪切可能发挥内在作用。细胞转变：当{111}<110>系统被激活时，形成是显着的，而当{100}<110>滑移系统被激活时，例如在较高温度下的蠕变破坏中，形成是可以忽略不计的。 (4)相变的增长成功地用Johnson-Mehl型方程表示。相变的增长必须受到Al和Ni扩散过程的控制，其中活化能由约36 kcal/mol决定。(5) ）这小疲劳裂纹扩展速率在转变区域显着增强。