Corrosion Resistance of Deep Rolled AISI 304L Using Cryogenic Cooling

Cryogenic deep rolling (DR) is an innovative technique combining different energy sources: mechanical and thermal. This treatment is used to enhance mechanical properties of materials. In the present work, The DR process under cryogenic cooling was performed at a different number of passes to assess the corrosion behavior in the chloride environment of the AISI 304L stainless steel (SS). The effects of cryogenic DR on the surface integrity (roughness, microstructure, surface residual stress levels as well as phase transformations) were experimentally evaluated. It was shown that the reduction of surface roughness, grain refinement formed in the top-surface layers and, highly compressive residual stress amplitudes generated by cryogenic DR of AISI 304L samples (at 2 and 3 passes) led to the enhancement of resistance to uniform and localized forms of corrosion regarding the machined ones. However, it was found that specimens treated at 4 passes exhibited the worst corrosion behavior. Under this condition, the arithmetic average roughness was reduced from 4.04 µm (Machined state) to 0.32 µm and a recrystallized structure with refined grains was generated in the topmost surface. Moreover, high levels of compressive residual stresses (up to −1157 MPa) were introduced in the surface layers. Nevertheless, the high amount of martensite (55%) annulled the beneficial effects of surface smoothing, grain refinement and compressive residual stresses and consequently deteriorated the corrosion behavior of AISI 304L SS in chloride solution.