Hybrid technology hard coating : Electron beam surface hardening

Abstract Hard surface layers often cannot show advantages of their good hardness, strength and wear resistance over relatively soft materials so that an additional thermal treatment of the base materials before or after coating is necessary. Surface treatment technologies with high energy beams {electron beam (EB) or laser beam (LB)} offer a good and modern alternative to the mostly used bulk heat treatment. The energy deposition is precisely focused, so it is possible to exactly limit the heat treatment to highly loaded areas and up to the depth where a transformation (hardening) is necessary. Therefore, the bulk materials are not heated up to critical temperatures. The thermal load of the overall component is minimized and thus distortion can also be avoided. The paper deals with current results of investigations on the combination of PVD hard protective coatings {based on Ti(C)N, TiAlN, Cr x N y and DLC} with electron beam surface hardening. Base materials used for these investigations were different steels (unalloyed steel: C45; low alloyed tool steel: 100Cr6; high alloyed tool steel: X155CrVMo12-1). It is not only the sequence of treatments (beam hardening before or after coating) which has a considerable influence on treatment results, but also the parameters of EB surface treatment (energy density distribution, speed of treatment, vacuum). It will be discussed the relations between treatment conditions, process parameters and surface deformation, layer structure and composition, structure and composition gradients, surface properties, properties gradients and transformation behavior of matrix materials. These modern combined technologies open up new fields of industrial application for tools and components subjected to locally high load.