喷丸强化对FGH4097粉末高温合金室温高周疲劳极限的影响

High Cycle Fatigue Limitation of FGH4097 P/M Superalloys by Shot Peening at Room Temperature

摘要:

本文对FGH4097粉末高温合金进行喷丸强化,测定室温下高周疲劳极限,利用SEM观察疲劳断口特征及喷丸表面形貌,X射线应力仪和超微小动态显微硬度仪测定试样表层残余应力σ_r和显微硬度H,采用EBSD及TEM观察喷丸强化层的微观特征。结果表明：室温下,与未喷丸试样相比,喷丸后残余压应力更大、更深和更稳定,有利于提高疲劳裂纹萌生抗力及降低裂纹扩展速率；且喷丸表层的高位错密度、大量小角度晶界及软取向晶粒数量减少阻碍疲劳裂纹在表面萌生, 从而FGH4097高周疲劳极限提高20.7%。

关键词:喷丸强化;FGH4097粉末高温合金;室温高周疲劳

Abstract:

Effects of shot peening on high cycle fatigue limitation of the powder metallurgical nickle-based FGH4097 superalloy at room temperature were investigated in this article. Fatigue fracture characteristics and shot peening surface morphology were observed by SEM, the sample surface residual stresses σ_r and microhardness H were determined by X-ray diffraction stress tester and ultra-small dynamic microhardness tester, and EBSD and TEM were used to observe the microscopic characteristics of the shot peening layer. The results show that compressive residual stresses induced by shot peening are more deeper and more stable than without shot peening, which is beneficial to improve the resistance of fatigue crack initiation and reduce crack propagation rate. And the high dislocation density, a large number of low-angle boundary and a small number of soft orientation grain in the surface layer of shot peening make the fatigue crack difficult to initiate at the surface. So, 20.7% increasing at high cycle fatigue limitation of the FGH4097 superalloy at room temperature.

Key words:Shot peening strengthen; P/M FGH4097 superalloys; high cycle fatigue limitation at room temperature