Influence of high cutting speed turning on surface and corrosion properties of 08Ch18N10T austenitic stainless steel from the perspective of operational safety of primary circuit of a nuclear power plant

From the point of view of the safety of nuclear power plants, it is necessary to determine the properties of the manufactured material used. One of the possible risks is the use of inappropriate turning on the material, whose subsequent surface and thus corrosion properties in such an extreme environment are significantly stricken. In this work, high cutting speed (596 m⋅min⁻¹) was used for turning austenitic stainless steel 08Ch18N10T using a CBN cutting tool. Such a high cutting speed significantly affected surface integrity and surface properties such as residual stresses, roughness, hardness and surface toughness (metallographically determined and analysed using X-ray tensometry and acoustic emission). The area that was turned contained deformed grains, which contained deformation twins and slip bands. All these factors can affect stress corrosion cracking susceptibility and corrosion resistance. For this reason, the sample was exposed in a MgCl2 solution according to the ASTM G36, while the surface crack density and the crack lengths or depths were determined. The effect of residual stresses on the direction and propagation of surface cracks has been proven. DL-EPR test recorded sensitization that did not occur at the grain boundaries but in the turning direction where pitting lines appeared. Exposure in a simulated primary circuit environment was performed in an autoclave, where no signs of stress corrosion cracking were confirmed.