Internal die cooling during forging can reduce thermal loads, counteracting surface softening, plastic deformation and abrasive die wear. Additive manufacturing has great potential for producing complex geometries of the internal cooling channels. In this study, hybrid forging dies were developed combining conventional manufacturing processes and laser powder bed fusion (L-PBF) achieving conformal cooling channels. A characterisation of the used hot-work tool steel’s AISI H10 powder material was carried out in order to determine suitable parameters for L-PBF processing and heat treatment parameters. Additionally, the mechanical properties of L-PBF-processed AISI H10 specimens were investigated. Furthermore, the influence of different internal cooling channels regarding a possible structural weakening of the die were analysed by means of a finite element method (FEM) applied to a hot-forging process. The numerical results indicated that the developed forging dies withstood the mechanical loads during a forging process. However, during the investigation a large dependency between the resulting stresses and the chosen parameters were observed. By choosing the best combination of parameters, a reduction of the equivalent stress by 1000 MPa can be achieved. Finally, a prototype of the hybrid-forging dies featuring the most promising cooling channel geometry was manufactured.

This paper presents the numerical design of a hot forging process for titanium Ti-6Al-4V. A steel-encasing made of AISI 316L is used to enclose the titanium and protect it from the surrounding gases and excessive cooling. Oxidation by the ambient gases can lead to a reduction in the mechanical properties of the titanium in the near surface regions. At the same time, costs and resources can be saved, as time-consuming reworking of the titanium and therefore the amount of reworking required can be reduced. Finite element simulation was carried out for efficient process design. For a realistic depiction of the process the coefficient of thermal expansion as well as the flow curves were determined in experimental tests. A numerical parameter study was carried out by varying process boundary conditions such as the starting temperature of the billet, the ram velocity and the thickness of the steel-encasing. The numerical results indicate that a steel-encasing of two millimetres at the top area of the billet, compared to four millimetres, is not recommended for the process due to a fracture in the steel-encasing. Overall, it was revealed that an increasing billet temperature results in a higher final temperature in the titanium and greater local thinning of the steel. The same tendency was also determined with increasing ram velocity. For the variants investigated here, the combination of a billet temperature of 1,100 °C and a medium ram velocity of 20-40 mm/s with a thickness of four millimetres of the steel-encasing at the top is recommended.

In the context of an ageing society, advancements in medicine and biomedical technology are becoming increasingly important. A major goal is to minimise the number of surgical operations. Magnesium alloys are gaining attention due to their degradable properties, good biocompatibility, and osteoconductivity. However, for implants made from this material to be usable, a precise understanding of the degradation rate and a correspondingly adapted design must be available. This work focuses on constructing a suitable experimental chamber for degradation analysis, as well as investigating the impact of sample positioning on degradation using two different geometries of WE43 alloy for potential use as osteosynthesis implants. Optical and mechanical tests were carried out on these geometries. The tests revealed that the sample positioning in the experimental chamber affects degradation, with the central position yielding the most suitable results for future applications. In addition, mechanical tests demonstrated reduced mechanical properties in the degradation layer. This work provides an initial basis for further investigations into the use of the WE43 alloy as an osteosynthesis implant and supports the numerical calculation of degradation.

-Numerical process design for the production of a hybrid die made of tool steel X38CrMoV5.3 and inconel 718 SIRING Janina, HEINE Christoph, TILL Michael, WE