Influence of Shot Peening Parameters on Residual Stresses in Flake and Vermicular Cast Irons

Abstract

Test samples of grey and compacted graphite cast irons with pearlitic matrix were shot-peened to different surface conditions using twelve different combinations of shot size, peening intensity and peening coverage percentage. Relatively high surface compressive residual stresses varying between 245 to 565 MPa were observed and the compressive residual stresses reached a depth between 280 µm and 770 µm. Within the range of peening parameters used, the compacted graphite cast iron with its vermicular graphite showed a somewhat better response to the same shot-peening treatment than the grey cast iron containing flake graphite, giving a larger peening affected zone with higher compressive residual stresses. For both the cast irons, an increase in peening coverage percentage, shot size or peening intensity led often to a lower surface compressive stress. However, peening using a higher intensity greatly increased the degree and extent of plastic deformation and therefore increased the magnitude and penetration depth of the subsurface compressive residual stresses, while the effect of increasing shot size also depends on the peening intensity. On the other hand, measurements on the grey cast iron samples showed that the peening coverage has little effect on the depth profile of residual stress.

Improvement in fatigue life of Al 7475-T7351 alloy specimens by applying ultrasonic and microshot peening

“…In the case of Microshot Peening the beads are bombarded into the material surface by a nozzle, and the main process parameters are the beads diameter, process intensity, exposure time, coverage, air pressure, impact angle and nozzle characteristics and all of them can be optimized [15][16][17][18]. Like in steels, literature shows that the major part of this improvement can be attributed to the compressive residual stresses in the surface region, which very often overcompensates the worsening of surface morphology [19][20][21][22][23].…”

Influence of Shot Peening on DIN 1.2714 Hot Work Tool Steel

“…With the same shot size, increasing intensity means a higher impact speed. Because of the increased kinetic energy, the degree of plastic deformation and its depth in the sample is significantly increased [13].…”

Experimental Investigation on the Effect of Shot Peening and Deep Rolling on the Fatigue Response of High Strength Fasteners

“…Previous studies [30][31][32][33][34] indicate that residual stress trends usually exhibit a sub-surface peak. For the shot-peening, the higher the shot diameter, the deeper the subsurface peak.…”