Effects of different alloying concepts of new hot work tool steels on the hardness profile after nitriding

Hot work tool steels contain several strong nitride forming elements such as Cr, V and Si that affect the nitriding of steels for many applications. The present paper presents the effects of different alloy compositions of hot work tool steels, including standard grades, new vacuum remelted high performance grades and some model alloys, on the hardness profile after nitriding. The effect of the content of different elements (Cr, Mo, V, Si and Al) on the maximum hardness level and the nitriding depth were investigated. Reducing the silicon content enhances the nitriding performance, resulting in a higher nitriding depth or shorter nitriding duration. Aluminium reduces the nitriding depth slightly but leads to a strong increase in the surface hardness. Furthermore, aluminium significantly improves the thermal stability of the nitrided layer under operating conditions. The results can be used to aid the selection of hot work tool steels and appropriate nitriding parameters.