Martensitic high nitrogen steel for applications at elevated temperature

Based on required material properties for inlet valves in combustion engines a martensitic high nitrogen steel was created. After selecting an alloy system with 14-17 w/o Cr, 1-3 w/o Mo, 0.1-0.3 w/o V and 0.4-0.7 w/o N by method of thermodynamical calculations of phase equilibria the newly developed martensitic steel was produced by pressurized electroslag remelting. Hot tensile tests and corrosion tests were carried out on hardened and tempered specimens in comparison with two standard valve steels. The high nitrogen steel shows a distinctly better corrosion resistance and high-temperature strength than the standard steel X45CrSi9-3 and is therefore comparable with the steel X85CrMoV18-2. Due to finer nitrides the newly developed steel is characterized by a fatigue strength which is 26% higher at 500 C service temperature. (orig.)