Surface treatment by electron beam in combination with other heat treatment technologies

Thermochemical treatment, and PVD as well as CVD hard coating are used for improvement the surface properties of tools and highly-loaded components and achieved a high level of industrial application. Each of these surface technologies is used to enhance surface hardness, wear and friction behavior, and, in some cases, corrosion resistance, but they are restricted, however, by physical, technical, and technological characteristics. Special loading conditions present a great challenge, as the load capacity of each of the surface layers produced is limited.

The combination of EB surface treatment with thermochemical treatment and/or PVD or CVD hard coating enables significant further improvement of the relevant properties of components.

The principle behind these duplex surface treatments is based on the improvement of the supporting effect of transformation layers produced by the EB surface treatment.  These surface layers increases the load capacity of the thermochemically produced layer and/or the deposited hard coatings by optimization the property gradients.

The success of the combined treatments depends, among other factors, on the material-specific selection of the appropriate EB technology (i.e. a solid- or liquid-state process), on the sequence of treatments (i.e. whether the EB process is performed before or after thermochemical treatment and/or hard coating), and the selected beam deflection technique. Combined treatments may be used for steels, cast irons and Al alloys.

This paper presents a survey about the history of the development and the state of the art of material scientific investigations, as well as the technical state of the art in this field. In connection with different examples of combinations of surface treatments, both the technological options and limiting factors are discussed.

Examples of industrial application are given, and a forecast for advanced fields of application for these innovative combined surface technologies is provided.