P 1180 – Modelling of multiple phase transitions in tool steels during additive processes
The additive production is characterized by a cyclic heat input through the structure of the individual layers and the subsequent quenching through heat discharge via the base body. In laser powder deposition welding, the heat input is particularly high and at the same time the build-up frequency is significantly higher than in powder bed-based processes. In the additive production of martensitic hardenable steels, cyclic heating and quenching can lead to multiple transformation of austenite martensite and to significant tempering effects of the martensite. Depending on the process parameters, considerable microstructural and thus hardness gradients occur within a component.
For the hot work tool steel X40CrMoV5-1, the resulting microstructure was intensively experimentally investigated after laser powder deposition welding and conclusions were drawn about the formation mechanisms. On this basis, a model was developed for the cyclic transformation of austenite martensite and the tempering effects of martensite. This model was integrated into an FE program for the simulation of additive production. This was used to simulate simple model components and compare them with experimental results regarding the hardness distribution.
Prof. Dr.-Ing. F. Vollertsen, Prof. Dr.-Ing. H.-W. Zoch, Prof. Dr. A. Schmidt