Effect of Cold Rolling on the Coffin–Manson Relationship in Low-Cycle Fatigue of Superalloy IN718

Abstract

The age-hardenable Ni-Fe-based superalloy IN718 exhibits a dual-slope Coffin-Manson (C-M) relationship during low-cycle fatigue (LCF). Effort was made to eliminate the dual-slope C-M relationship by introducing prior deformation. Peak-aged (PA) material was subjected to different degrees of cold reduction, and its LCF behavior was examined. Cold rolling is found to be highly effective in eliminating the dual slope and enhancing the fatigue life at low strain amplitudes. Cold rolling coupled with stress relieving (SR) treatment is found to further improve the fatigue life. The role of texture on the observed LCF behavior is analyzed and found to have no significant effect.

Effects of prior cold working on low cycle fatigue behavior of stainless steels, titanium alloy timetal 834 and superalloy IN 718: A review

“…(Figs. 2 (a) & (b)) Praveen and Singh [16] have studied the effect of cold rolling on superalloy IN718 (0.003C, <0.10Mn, <0.005P, 0.001S, 18.2Cr, 54.0Ni, 2.9Mo, 1.04Ti, 0.54Al, 5.01Nb, and Balance Fe) .The Coffin-Manson plots for the four different cold-rolled conditions along with that of the Peak Aged condition (two stage heat treatment : initially at 720°C for 2hrs followed by furnace cooling to 620°C,subsequently holding at this temperature for another period of 8hrs.,followed by air cooling) are shown in Figure 3. It can be seen that except in the Peak Aged-20%Cold Rolled condition, where there is dual slope, in the other cold-rolled conditions (Peak Aged-10% Cold Rolled, Peak Aged-5%Cold Rolled as well as Peak Aged-5%Cold Rolled-Stress Relieved (at 550°C for 1.5hrs., followed by cooling in air)), there is a linear C-M relationship.…”

“…Figure 4 represents a model for the above explanation. Praveen and Singh [16] have also studied the role of texture developed due to rolling, on the improvement in fatigue properties of the cold-rolled superalloy IN718. Figure 5 shows variation of maximum orientation distribution function (ODF) intensity with amount of cold reduction.…”

“…[12] Alloy IN 718 is one of those alloys that exhibit planar slip behavior. [13,14] However, very limited work has been done on the effect of prior cold work on LCF behavior of Titanium alloy Timetal 834 and the superalloy IN718.Most of the work on this aspect have been done by Vakil Singh et al [11,16] .…”

Low cycle fatigue behavior and fracture mechanism of a directionally solidified CM247 LC superalloy

“…On the other hand, the Coffin-Manson equation is used for the low cycle fatigue (LCF) regime and defines the reliance of fatigue life under isothermal loading on plastic strain amplitude 39,40 :…”

On the feasibility of nonlinear assessment of fatigue damage in hardened IN718 specimens based on non-collinear shear wave mixing

“…In all the fatigue tests conducted in this study, the cycling frequency was f cycle = 2 Hz and the load ratio ( min / max in LCF and min / max in HCF) was R = 0.1. The nominal life of the fully hardened IN718 material exposed to VLCF was estimated as N VLCF = 250 cycles [15][16][17][18]. Seven specimens were low-cycle fatigued (LCF) under more typical peak strain of max = 1.2%.…”