Influence of Nitrogen Atmosphere on Reduction Mechanisms of a High Strength Austenitic Steel

Paper i proceeding, 2012

High C+N-alloyed austenitic steels feature outstanding mechanical properties with tensile strength of more than 1000 MPa and uniform elongation up to 75 %. These properties are achieved by an optimal C/N-ratio. Cast production limits the nitrogen content, since the melt features a significantly lower solubility than the solid state. Current investigations aim to adjust the nitrogen content by sintering atmosphere in the steel FeMn19Cr17C0.4N0.3. The gas-solid interaction is crucial also for the reduction of surface oxides, especially those formed by chromium and manganese, which can deteriorate the toughness of the sintered part. This study clarifies the influence of nitrogen atmosphere on surface properties during the heating stage of the sintering cycle up to 800°C. Investigation was done by surface analytical techniques (XPS and HR-SEM). The influence of nitrogen atmosphere on reduction mechanism and the resulting impact on nitrogen uptake are evaluated under consideration of previous studies.