ESSC & DUPLEX 2019

Conventional martensitic stainless steels for use in bearings, stainless tools or cutlery require high carbon and chromium contents in order to achieve the desired properties. However, they are prone to precipitate coarse carbides, which is a drawback in strength and corrosion properties. High nitrogen martensitic stainless steels with a fine dispersion of carbides or nitrides, that show high strength and good corrosion properties, are produced by pressurized-eletro-slag-remelting (PESR) which is an expensive process. The aim of this research is to develop a high nitrogen martensitic stainless steel with a good combination of mechanical and corrosion properties, which can be produced by conventional route (electric arc furnace, hot rolling, and subsequent heat treatment). A heat was cast, forged to bars and subsequently heat treated. The effect of hardening and tempering temperature on the mechanical and corrosion properties were studied. Hardening was carried out at temperatures between 900 and 1100°C for 30 minutes and quenched in water. Some specimens were deep freezed by -80 °C immediately afterwards. Tempering was carried out at temperatures between 160 and 760°C. Mechanical properties were determined through tensile, impact toughness and hardness (HRC). Corrosion properties were investigated in terms of rate of mass loss (ASTM ASTM G48 Practice A) and pitting corrosion resistance with potentiondynamic polarization technique (ASTM G61). The microstructure was characterized by optical and electronic microscopy and X-RD. The steel showed a fine martensitic microstructure with uniform dispersion of carbides. Hardening temperature has an influence on the microstructure and hardness. Increasing hardening temperature decreases hardness due to the high content of retained austenite. High nitrogen martensitic stainless steel shows a good combination of hardness, toughness and corrosion properties, with a room temperature UTS level of up to 2000MPa. These optimal mechanical and corrosion properties can be achieved with the correct selection of the heat treatment parameters.