Reproducible manufacturing of near-net-shape components by sintering with the consideration of large shrinkage
The influence of the density inhomogeneity of the green parts on the anisotropic sintering shrinkage has already been intensively investigated experimentally, but the initial density distribution has mostly been neglected in simulation. Therefore, the anisotropic sintering shrinkage cannot be correctly predicted by simulation programs which are available for industry. Since the precise and reproducibly adjustable sintering shrinkage is a decisive quality feature for many applications, the existing modelling approaches are not sufficient.
In the previous project IGF 19802 BG, only the isotropic sintering shrinkage was considered in the implemented sintering model. With the consideration of the influencing factors friction and gravity in the sintering simulation, the verified sintering model enables a precise prediction of the sintering behaviour of metal injection moulded (MIM) components (X2CrNiMo17-12-2) and the sintered cemented carbide components. For Binder Jetting (BJT) components (X5CrNiCuNb17-4-4), the accurate prediction of the final geometry could be achieved by implementing anisotropic factors into the sintering model. In addition, the prediction accuracy should be further improved by considering the local density and local shrinkage of the green parts during sintering. The improved simulation tool should allow the optimization of complex shaped green bodies, whereas previously only simple geometries were demonstrated.
Within the scope of the project, the near-net-shape production of sintered components is to be realized. The previously developed method can be transferred to the BJT, fused filament fabrication (FFF), MIM and conventional pressing sintering manufacturing routes, which will be demonstrated using various materials. Considering the material properties and density inhomogeneities of the green parts introduced by the various shaping processes, fundamental investigations of the sintering kinetics are to be carried out, which can also provide further information on the anisotropic shrinkage that occurs. Furthermore, the material properties that are relevant for the sintering behaviour will be determined experimentally and used in numerical simulations of the sintering process. Finally, the sintering models will be used to iteratively optimize the geometry of selected demonstration components in the green part condition, so that the geometry resulting after sintering corresponds to the desired target geometry. The numerical optimization in conjunction with an in-depth understanding of the correlation of individual process parameters also enables the extension of the existing portfolio of products for the manufacture of complex-shaped components, which could not previously be produced by powder metallurgical route, due to the large distortion that occurs.Copyright: © IWM
Fraunhofer IFAM, DresdenCopyright: © BMWK & FSV
IGF project 22261 BG of the Forschungsgesellschaft Stahlverformung e.V. was funded by the German Federal Ministry of Economic Affairs and Climate Action via the AiF as part of the program of joint industrial research (IGF) on the basis of a decision of the German Bundestag.