Volume 73, Issue 4

The tool steel AISI H13 is characterized by a high wear resistance and a good thermal shock resistance. H13 is mainly employed in applications such as tools for pressure die casting and forging. Processing of H13 by additive manufacturing techniques, such as selective laser melting (SLM), opens up new design possibilities with respect to e. g. internal cooling channels, in order to improve the tool performance during operation. However, due to high surface roughness and insufficient geometric accuracy imposed by SLM, additional cutting or forming processes are often required leading to an alteration of the surface and subsurface properties of the part. The presented work reveals the effect of SLM processing and subsequent face milling and/or deep rolling operations on the development of surface and subsurface properties and highlights adequate process windows.

Additive manufacturing (AM) methods become more and more important due to improvements in the printing technology and availability of printers. As additive manufacturing is still a very expensive technology, it is predominantly used for complex parts in aerospace or medical applications. Especially in such demanding applications the properties of the parts are very important. In case of M50NiL, a carburizing heat resistant steel typically used for mainshaft bearings in aero engines, the development of an AM process and the properties of AM processed parts are shown. By comparison with specimens manufactured from conventional M50NiL it is demonstrated, that properties determined by optical microscopy, hardness testing, tensile testing, and rolling contact fatigue testing of M50NiL AM and M50NiL conventional manufactured are comparable.

Inductive surface hardening falls under the standard heat treatment of automobile drive train components. Wheel hubs, kingpins and various axle shafts will, for instance, be hardened. Two different inductor concepts are generally used for such processes: ring or line inductors. Many geometric boundary conditions must be taken into account when line inductors are used. The adjustment of the hardness transitions of a component includes the length of the inductor and also, for instance, the arrangement of the supply leads. The use of field concentrators will also have a significant effect on the result. This article deals with tests and numerical calculations for a sample component on which these effects were examined.

During forging the tools have to resist high thermal and mechanical loads. Therefore, forging dies are usually nitrided in order to increase the wear resistance of the surface areas. Compared to nitriding carbonitriding increases the hardness depths in shorter treatment times. Due to the (carbo-)nitriding, the surface near region gets a better hot hardness and a better wear resistance than the untreated material. In a second process step by nitriding after carbonitriding, a wear and corrosion resistant compound layer can be created at the surface. In the present work the wear behavior of carbonitrided and nitrided hot working steel ENX38CrMoV5-3 (1.2367) was investigated. The evaluation concerning abrasion and thermal fatigue in the contact of forging die and workpiece was carried out by model wear tests like the two-disc test (Amsler test), the ball-on-disc test and a cyclic induction heating and quenching. The conditions of the heating cycles were chosen close to the forging process. The surface areas were investigated after several cycles in order to gain information about the mechanisms of the surface modification. Finally, the treatment combination carbonitring/nitriding was transferred to forging dies and the wear behavior was investigated in fatigue-life experiments under application conditions.

The increasing demands of the desire for even more high quality products in terms of lower weight, compact design and higher resistance towards stresses require the optimization of existing products through further developments. By combining of two or more materials, for example high-strength steel and aluminium, to one compound hybrid solid components can be manufactured with locally adapted properties and functions. The cutting process as the final step in the process chain significantly influences the performance and lifetime of such components through the produced surface and subsurface properties. The choice of a suitable tool for setting defined subsurface and surface properties turns out to be very difficult and has not been investigated sufficiently for hybrid components so far. The tool should generate the highest possible compressive residual stresses in the component with good surface quality. Therefore, this paper investigates and discusses the influence of different inserts with varying cutting nose radii as well as substrate and coating materials on process forces, process temperatures and surface roughness.