低膨胀GH2909合金缺口敏感性问题分析

Analysis on Notch Sensitivity of Low Thermal Expansion Superalloys GH2909

针对攀长特所生产的GH2909合金棒材在高温持久性能测试中出现缺口敏感的问题,分别对进口和国产GH2909合金的化学成分、显微组织和力学性能进行了对比,并对国产GH2909合金的锻造及热处理全流程中的组织演变进行了分析,揭示了国产GH2909合金缺口敏感性产生原因。研究结果表明:进口与国产GH2909合金成分基本无差异,但组织和性能差异明显;国产GH2909合金棒材由于锻造工艺不合理,造成组织中Laves相在晶粒内部的杂乱分布是其产生缺口敏感的关键原因。基于研究结果提出了改进锻造工艺,通过提高终锻温度,控制合金发生再结晶并使Laves相沿晶界析出,成功制备出组织性能优异的GH2909合金棒材,解决了国产GH2909合金棒材缺口敏感的问题。

Superalloy GH2909 bars produced by a Chinese supplier present high notch sensitivity during high temperature creep performance test.In order to understand the reason for this issue,the imported and studied GH2909 alloy bars had been compared in terms of their chemical compositions,microstructures and mechanical properties,and the microstructure development of studied alloy during processes from forging to heat treatment had been investigated as well.Chemical composition analysis results showed there was no apparent difference between imported and studied alloys.However,microstructure observation indicated two alloys present remarkable difference.For the studied alloy,the notch sensitivity is attributed to the random distribution of Laves phase inside the grain,which is expected to be caused by the inappropriate forging process.Based on the research results,an improved forging process was proposed. By increasing the final forging temperature,controlling recrystallization of the alloy and precipitating Laves phase along the grain boundary,a new GH2909 alloy bar with suitable microstructure and excellent properties was successfully prepared,and the problem of notch sensitivity of domestic GH2909 alloy bar was solved.