Microstructural and Tribological Characterization of Atmospheric Plasma-Nitrided HS6-5-2C Tool Steel

Abstract

The nitriding process is well known as a method to improve wear, strength and corrosion characteristics of materials surface. The Institute of Materials Science of Leibniz Universität Hannover is on a stage of development of a new nitriding process under atmospheric conditions. The main purpose of the research work is formation of a nitrided layer on the locally loaded areas of a tool (e.g. forging die) under atmospheric conditions to increase wear resistance and durability of operating tools. Nitride layers were generated on the tool steel HS6-5-2C using the transmitted plasma arc. After atmospheric plasma nitriding the samples were investigated using optical microscopy, transmission electron microscopy (TEM), X-Ray diffraction (XRD) and microhardness testing techniques. It has been revealed that the modified zone thickness after atmospheric plasma nitriding reaches 200 μm. TEM and XRD analysis have shown that new phases corresponding to iron nitrides were formed in the surface zone. Microhardness of the surface layer is increased by 10% and friction coefficient has been reduced by approximately 50% in comparison with base material.