High Nitrogen Austenitic Cases in Stainless Steels

摘要

Utilizing the high nitrogen solubility of the austenitic phase nitrogen can be introduced into the surface of a near net shape part by a new diffusion process called "solution nitriding". The result is a fully austenitic case around a martensitic, austenitic-ferritic or austenitic core as depicted in the Schaeffler diagram. This high strength yet very tough high nitrogen case shows improved wear and corrosion properties. Especially the wear rate by cavitation is extremely reduced because of a different strengthening behavior as compared to conventional steels. As long as nitrogen is totally dissolved in the case the corrosion properties are not impaired. The formation of nitrides during solution nitriding, which consume chromium and in consequence lower the corrosion resistance, can be beneficial for applications under mainly erosive loading.