Effects of cutting parameter on microstructure and corrosion behavior of 304 stainless steel in simulated primary water

Abstract

• Cutting can induce a gradient surface microstructure with a several microns deep fine-grain layer on top, followed by several tens or hundreds of micrometers deep plastic deformation region. • Even with the similar surface roughness, the deformation microstructure can be very different due to the different cutting parameters. • The effect degree on the depth of machining-affected zone (MAZ) is feed rate > cutting depth > cutting speed. • At the same depth of MAZ, the localized corrosion rate along the deformation bands is higher than that along the grain boundaries. The influence of surface conditions on the corrosion behavior of engineering structures has been paid more attention. However, there is still a lack of systematic research on the effect of cutting parameters on material's microstructure and performance in service. In this paper, the effect of cutting parameters on microstructure and corrosion behaviors of 304 stainless steel in simulated primary water is well investigated. The results show that different cutting parameters can cause the superficial layer a gradient microstructure with nanocrystalized layer on top and deformation band structures underneath. With the similar surface roughness, the deformation microstructure can be very different due to the different cutting parameters. The effect degree on the depth of deformation zone is feed rate > cutting depth > cutting speed. The larger feed rate, lower cutting depth, lower cutting rate may induce a deeper deformation zone. With the increasing depth away from the machined surface, the localized corrosion rate is decreased, and at the same depth the localized corrosion rate along the deformation bands is higher than that along the grain boundaries (GBs). The nanocrystalized surface has a smallest general corrosion rate due to the quick formation of Cr rich oxide film. However, once the corrosion penetrates through this nanocrystalized layer, subsequent preferential corrosion at deformation bands and GBs will dominate and may lead to the significant increase of corrosion rate of the component in high temperature pressurized water.