Characterization of ultrasonically peened and laser-shock peened surface layers of AISI 321 stainless steel

Engineering the residual stress state and microstructure of stainless steel with mechanical surface treatments

“…Investigations on 321 stainless steel by Mordyuk et al observed DIM in ultrasonically peened samples but not for LSP samples [17]. The absence of martensite was attributed to the temperature increase generated by the ablation process [17]. The presence of DIM found in the LSP sample examined in this paper may be attributed to the use of a metallic protective tape combined with a film of running water during peening.…”

“…The presence of DIM has been reported for deep rolling treatment of 304 stainless steel [16]; however, none was observed for LSP for the reported process parameters [16]. Investigations on 321 stainless steel by Mordyuk et al observed DIM in ultrasonically peened samples but not for LSP samples [17]. The absence of martensite was attributed to the temperature increase generated by the ablation process [17].…”

“…The presence of the tape and water is believed to prevent localised heating during the LSP process. No mention of the use of a protective metallic film or water could be found in the LSP process parameters described in [16] or [17]. The susceptibility of a given stainless steel alloy to DIM is thought to be related to the stacking fault energy (SFE) [18].…”

“…LSP involves the generation of plastic deformation to the surface layers through laser-driven shock waves, generating compressive residual stresses to up to several millimetres in depth. The shock waves are produced from the confined, rapid expansion of a plasma generated by the irradiation of the surface (with or without a sacrificial coating) by a high power laser pulse [3,10,11]. The effectiveness of LSP for steels has been demonstrated through preventive maintenance against stress-corrosion cracking in operating nuclear power reactors since 1999 [12].…”

Formation of Surface Nano/Ultrafine Structure using Deep Rolling Process on the AISI 316L Stainless Steel

“…Therefore, surface properties such as hardness must be improved using appropriate techniques. Mechanical surface treatments such as ultrasonic shot peening, 3,4 laser shock peening, 5,6 burnishing 7,8 and deep rolling 9,10 are appropriate methods for surface grain refinement, resulting in improvement of surface hardness and other properties of austenitic stainless steels. Among them, deep rolling is a well-known method for increase of surface regions hardness with a thick affected depth.…”