The near surface area of forging dies is exposed to high mechanical loads. Additionally thermal and chemical stresses appear during the hot forging process. Depending on the number of forged parts, several kinds of stresses occur in the near surface area, which lead to the initial failures of forging dies. Wear is the main reason for production downtimes with a ratio of 70%. Furthermore, thermal and mechanical cracks are typical causes for failures causes as well as plastic deformation. In order to reduce wear, the abrasion resistance of the forging die surface has to be increased. Hence, different methods like plasma nitriding and optional additional thin hard coatings (TiN, TiCN, TiC, TiBN and TiB2) were successfully examined. Recently developed Ti-B-N coatings in specific multilayer designs are thermally stable, wear-resistant and anti-adhesive regarding the sticking of work piece material. This paper presents the wear reduction possibilities of boron-containing mult ilayer coating systems applied to forging dies by using the plasma enhanced chemical vapor deposition treatment. A basic mechanical and analytical characterization of different coating systems is realized in the first stage of the project. Best qualified multilayer coating variants were applied to forging dies for experimental investigations. As a result of the tests, wear can be reduced significantly by using thermally stable boron multilayer coatings. To receive realistic wear values under production conditions, an automated forging process was used for testing. After 3,000 forged parts, the coatings were examined by tactile measurement, SEM and EDX analyses to characterize the occurring wear

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The demand for economic processes concerning manufacturing technology, cycle time and material properties has led to the development of near net-shape techniques. Precision forging is a well-known manufacturing technology to achieve high output rates. An approach of optimization concerning the part material to produce load-adapted material properties is the so-called compound-forging. Therefore, two different alloys are forge-welded together. Non-tempering and tempering steels are used to compound-forge gears with a hard and wear-resistant surface layer as well as a ductile bulk material. Compound-forging was developed to forge spur gears and shall now be introduced to manufacture helical gears and shafts. For the production of gears and shafts billets made from non-tempering steels are forge-welded together with billets consisting of tempering steels by precision forging as well as indirect impact extrusion. In this paper, the comparison of the material properties of compound-forged gear wheels and shafts with a hard and wear resistant surface layer and a ductile bulk material is given. Mechanical properties as well as the micro-structure of the parts were investigated. The results of the investigations show a load-adapted material distribution of forge-welded materials for the production of gears and shafts.

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