Influence of residual stresses on the fatigue crack growth from surface anomalies in a nickel-based superalloy

On the conjoint influence of broaching and heat treatment on bending fatigue behavior of Inconel 718

“…They also found that a short time heat treatment on the machined alloy resulted in an even better fatigue resistance, but a prolonged heat treatment either led to no improvement or a decrease of the fatigue life. The beneficial effect of compressive residual stresses have also been reported in other nickel-based superalloys [17][18][19].…”

Effects of Machining Induced Residual Shear and Normal Stresses on Fatigue Life and Stress Intensity Factor of Inconel 718

“…It is noteworthy that, among the surface integrity factors, residual stress plays a key role in affecting the fatigue performance of components [3][4][5][6]. Compressive residual stress (CRS) is beneficial to improving fatigue performance [7][8][9], whereas induced tensile residual stress is usually detrimental to the fatigue life of components [10,11].…”

Assessment of specific contribution of residual stress generated near surface anomalies in the high temperature fatigue life of a René 65 superalloy

“…Scratches and dents have a depth of 150 μm and a length of 3 mm. They are introduced using a carbide tool with a controlled and reproducible manner described in a previous publication 13 . Table 1 presents the average geometrical dimensions of scratches and dents (over 12 of each anomaly).…”

“…Conversely, evaluating the effects of a residual stress field induced by an anomaly on the low cycle fatigue life is not as simple because residual stresses are difficult to predict, while they control the initiation as the fatigue crack growth, causing an acceleration or a slowdown of propagation depending on the nature of the stress (tensile or compressive) 3 . Indeed, residual stresses are not constant over time and can release more or less rapidly depending on the material, temperature and loading conditions but also due to crack propagation 11,12 . Recently, the use of a relaxation heat treatment evidenced the influence of the residual stress field because of the introduction of maintenance surface anomalies in the Direct Aged 718 nickel based superalloy 13 , especially during the early stages of the crack propagation. In addition to the initial residual stress field, Frankel and al have also highlighted the importance of characterising the relaxation and redistribution of residual stresses during a fatigue test 9 also studied by means of numerical simulations near a V-notch tip by Ferro 10 .…”

“…Recently, the use of a relaxation heat treatment evidenced the influence of the residual stress field because of the introduction of maintenance surface anomalies in the Direct Aged 718 nickel based superalloy 13 , especially during the early stages of the crack propagation. Indeed, it was observed that the complex field below surface anomalies is responsible for a delay in crack growth, in comparison with the growth rate of a long crack and that residual stresses strongly influenced the evolution of the crack front shape.…”