GH4169合金高溫疲勞裂紋擴展的微觀損傷機制

侯杰; 董建新; 姚志浩

doi:10.13374/j.issn2095-9389.2018.07.008

GH4169合金高溫疲勞裂紋擴展的微觀損傷機制

doi: 10.13374/j.issn2095-9389.2018.07.008

北京科技大學材料科學與工程學院, 北京 100083

基金項目:

國家自然科學基金資助項目(51371023)

詳細信息

中圖分類號: TG146.1
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出版歷程
- 收稿日期: 2017-06-28

Microscopic damage mechanisms during fatigue crack propagation at high temperature in GH4169 superalloy

School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China

摘要

摘要: 空氣環境對高溫合金在高溫下的損傷行為有顯著影響.為了研究標準熱處理態GH4169合金在高溫疲勞裂紋擴展過程中的微觀損傷機制,在空氣環境中進行650℃、初始應力強度因子幅ΔK=30 MPa·m^1/2和應力比R=0.05的低周疲勞裂紋擴展試驗.使用掃描電鏡(SEM)及能譜(EDS)對試樣的斷口、外表面和剖面進行觀察和分析.實驗結果表明:疲勞主裂紋以沿晶方式萌生并擴展,隨后沿晶二次裂紋出現,并且其數量和長度沿主裂紋方向逐漸增加,進入快速擴展階段后,斷口呈現韌窩組織形貌;在裂紋擴展過程中,δ相與基體的界面發生氧化,使得沿晶二次裂紋沿界面擴展并產生偏折,從而起到阻礙二次裂紋擴展的作用;試樣外表面的主裂紋周圍出現晶界氧化損傷區,其尺寸和晶界開裂程度沿主裂紋擴展方向逐漸增大.
- GH4169合金 /
- 高溫 /
- 裂紋擴展 /
- 晶界氧化 /
- δ相
Abstract: The air environment strongly influences the damage behaviors of superalloys at high temperatures. To investigate the microscopic damage mechanisms during high-temperature fatigue crack growth in standard heat-treated GH4169 superalloys, low-cycle-fatigue crack growth tests were conducted at 650℃ with initial stress intensity factor ΔK=30 MPa·m^1/2 and stress ratio R=0.05 under the air environment. The fracture surface, outside surface, and central sectioned surface of the specimen were observed and analyzed using scanning electron microscopy (SEM) and energy-dispersive spectrometry (EDS). The results show that the main fatigue crack initiates and propagates intergranularly, followed by the appearance of intergranular secondary cracks, whose quantity and length increase along the propagating direction of the main crack. In the rupture stage, a dimpled morphology appears on the fracture surface. Oxidation occurs at the interfaces between δ phases and the matrix during the fatigue crack propagation process, which leads to secondary cracks propagating along the interfaces. This leads to their inflection, which in turn retards their propagation. A grain-boundary oxidation damage zone exists at the outside surface of the specimen near the main crack. The size and degree of grain-boundary cracking increase along the propagating direction of the main crack.
- GH4169 superalloy /
- high temperature /
- crack propagation /
- grain boundary oxidation /
- δ phase

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