Transformations Induced in Austenitic Stainless Steels by Shot Peening

Author:  D Kirk
Source:  Conf Proc: ICSP-7 (pg 15-22)
Doc ID:  1999011
Year of Publication:  1999
Abstract:  
The presence of martensite in a nominally austenitic stainless steel can have a profound effect on the steel's physical, chemical, mechanical and service properties. Plastic deformation can induce transformation of austenite to martensite. AISI 304 and 316 steels were peened using a broad range of peening severities. Peened and unpeened specimens were examined using 'direct comparison' XRD, 'two-exposure' XRD, hardness surveys, metallography and qualitative corrosion testing. The 304 grade was found to contain approximately 50% or martensite after peening with high levels of compressive residual stress in both austenite and martensite phases. No transformation was observed in the 316 grade. Hardening by peening occurred to similar depths in both grades but the degree of surface hardening was much higher in the 304 grade (750HV cf 550HV). Corrosion tests showed that the two-phase, peened, 304 grade had a substantially reduced corrosion resistance as compared with the single-phase, peened, 316 grade.