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本文研究了喷丸强化对提高一种铁基高温合金疲劳性能的作用,并着重考虑了在温度和交变应力的长期作用下由于应力弛豫而引起的强化效果的改变。实验中发现,喷丸处理显著地提高了这种铁基高温合金的疲劳强度,当存在应力集中时效果更为明显。但高温和交变应力的长期作用能够造成残余压应力的弛豫,导致强化效果的逐渐降低。用X-射线衍射仪和“弧高法”研究了不同温度下(400°、600°、700℃)的应力弛豫过程。断口分析指出喷丸处理显著地增加了试样的表面强度,延缓了裂纹沿表面的扩展速度。工作中还对喷丸后试样的高温持久强度及喷丸与未喷丸区域界面的作用进行了少量的实验。综合这些结果,作者认为当零件以疲劳为主要破坏形式时,这种合金喷丸强化的有效上限温度可达700℃;如果零件主要受到静态应力的作用,蠕变断裂是主要破坏形式时,在650℃以上就不宜采用喷丸处理。至于中温和常温区,喷丸强化对改善这种合金的疲劳性能,降低合金的缺口敏感程度,提高零件工作的可靠性都是十分有利的。
In this paper, the effect of shot peening on improving the fatigue properties of an iron-based superalloy was studied, and the strengthening effect due to stress relaxation under the long-term action of temperature and alternating stress was mainly considered. It was found in the experiment that shot peening significantly increased the fatigue strength of this iron-based superalloy and that the effect was more pronounced in the presence of stress concentration. However, the long-term effects of high temperature and alternating stress can cause the relaxation of residual compressive stress, resulting in the gradual decrease of strengthening effect. The stress relaxation process at different temperatures (400 °, 600 °, 700 ° C) was investigated by X-ray diffraction and “arc height method”. Fracture analysis indicates that shot peening significantly increases the surface strength of the specimen and retards the rate of crack propagation along the surface. The work also carried out a small amount of experiments on the high temperature lasting strength of the shot after shot peening and the effect of the interface between shot peening and non-shot peening. Based on these results, the author thinks that the effective upper limit temperature of shot peening can reach as high as 700 ℃ when fatigue fatigue is the main part of the part. If the part is mainly subjected to static stress and the creep rupture is the main failure mode, 650 ℃ above should not be shot peening. As for the moderate temperature and normal temperature, shot peening to improve the fatigue properties of this alloy, reducing the sensitivity of the gap of the alloy, improve the reliability of part work are very beneficial.