**1. Introduction**

In many technical applications, functional part regions of components experience a significantly higher load than basic structural regions. This occurs, for example, due to rolling contacts, like rolling bearings or gears. The material at and just below the surface, such as the raceway of the bearing, can experience very high stresses of over 3000 MPa and exceed 10<sup>6</sup> load cycles. In order to achieve a long lifetime, the material needs to be of a high quality, strength, and hardness. Mounting components such as shafts or less stressed regions in gear wheels like the connecting structure between the hub and teeth are subjected to a much lower load. Depending on the application, a base material with reduced strength or a lighter material may be su fficient or even advantageous.

Especially in large size bearings, the material costs for high purity steels that are mostly free of tramp elements are very high. Thus, a compromise between costs and benefit has to be made. The localized application of a layer of a high-performance material in the highly loaded area improves the mechanical properties where these are required. A base material, which is located in the less highly loaded region, can save costs and can fulfill other functions regarding, e.g., weight reduction or a modified ductility. These multi-material components can be adapted to thermal, environmental, and mechanical stresses depending on the application.
