Martensite residual stress

Welding carbon and low-alloy steels can create residual stress and cause undesirable microstructure changes, e.g., formation of martensite, both of which make steel more vulnerable to hydrogen embrittlement. - - Both the fusion zone and heat-affected zone regions of the weld can have microstructures that vary from the base metal. 

Fig. 3 Residual stress profile at different process conditions resultant from transformation of ferritic-perlitic to martensite phase after grind hardening (After Brockhoff and Brinksmeier 1999, with permission from Elsevier)...

It has long been recognized worldwide that also a cold work process particularly severe can contribute to corrosion in austenitic stainless steels by sensitizing the material [15-19]. Grinding must be completely rejected, in particular when high speed without lubricant is used. The sensitization process is due to two simultaneous actions. First, any heavy cold-working may leave a system of traction residual stresses (see Sect. 3.4 and Fig. 3.11) that favor stress corrosion. Secondly, plastic deformations induced by cold working may transform part of the metastable austenite into brittle martensite. 

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