Surface layers for hot working steels

Laser beam alloying of forging and diecasting tools with additional materials has proved in industry its ability to modify the chemical composition and thereby the properties of the surface layers. This results are a manifold increase in tool life. Relying on this knowledge, new surface layers for tools and components were systematically developed with the help of theoretical thermochemical models. On extrusion die tools the strain is very high due to the long contact time at a high temperature. For these tools a surface modification by molybdenum (Mo), tungsten (W), cobalt (Co) and vanadium (V) offers interesting combinations. For example, the additional alloying With Mo and vanadium carbide (VC) through alloying significantly increases the tool hardness retention, high temperature-hardness and hot wear resistance. The pre and post heat treatment can optimise the characteristics of this new surface layers, as well as the combination of laser treatment and nitride hardening. Also the s tructure, the hot wear resistance and the hardness at high temperatures of this layers were analysed and some results of industrial applications will be given. This contribution will contain the scientific and fundamental characteristics of surface layers produced in this manner, as well as their analysis with regards to operational properties.