Effect of shot peening on fatigue strength of DED-Arc steel specimens with as-built surfaces

This screening study investigates the effect of shot peening and blast cleaning on the fatigue strength of additive manufactured steels structures by directed energy deposited-Arc (DED-Arc) with as-built surface condition. Specimens were manufactured from low-alloyed, low-alloyed high-strength, and austenitic stainless steel wire feedstock. Following specimen preparation surface peening was applied and specimens were characterized regarding surface topography, residual stress condition, hardness and microstructure. Fatigue tests were conducted with constant amplitude axial sinusoidal loading at a stress ratio of R = 0.1. The fatigue test results are further compared to specimens in as-built condition as well as milled DED-Arc specimens. It was found that shot peening led to fatigue strength improvement for all considered steel materials with the degree of improvement depending on the steel grade. Furthermore, the results indicate an influence from shot peening intensity on the increase in fatigue strength improvement, with lower peening intensity showing a less severe effect. The increase in fatigue strength due to shot peening can be linked to cold work hardening and the formation of compressive residual stress in the surface layer. Depending on the material, surface, and peening conditions, fatigue strength improvement of + 22–136% relative to the as-built condition could be determined after shot peening.