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Environment assisted crack growth in nickel-base superalloys at elevated temperature.

机译：在高温下，环境有助于镍基高温合金的裂纹扩展。

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摘要

The environmental effect on the fatigue crack growth rate of Ni-base superalloys at elevated temperature was evaluated in this study. A set of crack growth tests was performed on the turbine disk alloy ME3 at 704°C (1300°F) in vacuum and in air at 0 and 10 second hold times using two microstructures developed with two different cooling rates from the solution heat treat temperature. Fatigue crack growth tests were also conducted at 25°C (77°F) with the two microstructures. Also, a set of oxidation experiments was conducted in order to evaluate the high temperature oxidation behavior of ME3. The microstructure was analyzed and the main differences between the two cooling rates were in the amounts of minor phase particles and size of secondary gamma prime particles. The crack growth rate results suggest that there is no measurable effect of environment or microstructure at room temperature. For the tests conducted in air at elevated temperature, both hold time and microstructural effects were evident. A coupling effect was also observed between the microstructure and the environment. The samples that were slow cooled, and had larger secondary gamma prime particles, had slower crack growth rates and less intergranular fracture in air than the fast cooled samples. A possible explanation for this would be excess free chromium available along grain boundaries due to its low solubility in gamma prime, providing for greater oxidation resistance. An elevated temperature fatigue crack growth rate model for Ni-base superalloys is also proposed.
机译：在本研究中，评估了环境对镍基高温合金疲劳裂纹扩展速率的影响。使用两个微观结构对固溶热处理温度进行了两种不同的冷却，在704°C（1300°F）的真空和空气中，在0和10秒的保持时间下，对涡轮盘合金ME3进行了一组裂纹扩展测试。 。还在25°C（77°F）时对两种微观结构进行了疲劳裂纹扩展测试。此外，进行了一组氧化实验，以评估ME3的高温氧化行为。分析了微观结构，两种冷却速率之间的主要区别在于次要相颗粒的数量和次级γ初生颗粒的尺寸。裂纹扩展速率结果表明，室温下没有可测量的环境或微观结构影响。对于在升高的温度下在空气中进行的测试，保持时间和微观结构效果均显而易见。在微观结构和环境之间也观察到耦合效应。与快速冷却的样品相比，缓慢冷却的样品具有较大的次级γ初生粒子，其在空气中的裂纹扩展速率较低，并且在晶界处的断裂较少。对此的一种可能的解释是，由于其在γ射线中的溶解度低，沿晶界可利用的游离铬过多，从而提供了更高的抗氧化性。还提出了镍基高温合金的高温疲劳裂纹扩展速率模型。

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  • 作者

    Evans, Jeffrey Lee.;

  • 作者单位

    University of Arkansas.;

  • 授予单位 University of Arkansas.;
  • 学科 Engineering Mechanical.;Engineering Materials Science.;Engineering Metallurgy.
  • 学位 Ph.D.
  • 年度 2008
  • 页码 135 p.
  • 总页数 135
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 机械、仪表工业;冶金工业;工程材料学;
  • 关键词

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