Influence of Machining on the Microstructure, Mechanical Properties and Corrosion Behaviour of a Low Carbon Martensitic Stainless Steel

The influence of cutting conditions of a low carbon martensitic stainless steel (15.5 wt.% Cr, 4.8% Ni, 1% Mo, 0.9% Mn, 0.24% Si, 0.1% Cu, < 0.06% C and 77.46% Fe) on the microstructure is first studied using electron backscatter diffraction and transmission electron microscopy. The mechanical and corrosion behaviours of this stainless steel are then investigated. It was found that the microstructure is significantly affected near the machined surface. The formation of grain sub-boundaries or a refinement of the microstructure is observed depending on cutting conditions. Both lead to an increase of the hardness. In addition, the microstructure refinement yields to a huge increase of the average pit surface area. By contrast the average pit density is not affected by machining conditions.