In this investigation, the fabrication of functionally graded structures of SS316L to Ni-based alloys were studied, using the novel technique 3D plasma metal deposition. Two Ni-based alloys were used, a heat resistance alloy Ni80-20 and the solid-solution strengthened Ni625. Different configurations were analyzed, for the Ni80-20 a hard transition and a smooth transition with a region of 50% SS316L/50% Ni80-20. Regarding the structures with Ni625, a smooth transition configuration and variations in the heat input were applied. The effect of the process parameters on the geometry of the structures and the microstructures was studied. Microstructure examinations were carried out using optical and scanning electron microscopy. In addition, microhardness analysis were made on the interfaces. In general, the smooth transition of both systems showed a gradual change in the properties. The microstructural results for the SS316L (both systems) showed an austenite matrix with δ-phase. For the mixed zone and the Ni80-20 an austenite (γ) matrix with some M7C3 precipitates and laves phase were recognized. The as-built Ni625 microstructure was composed of an austenite (γ) matrix with secondary phases laves and δ-Ni3Nb, and precipitates M7C3. The mixed zone exhibited the same phases but with changes in the morphology.
Additive manufacturing of titanium components offers several advantages compared to conventional production technologies such as higher material utilization efficiency and increased geometric possibilities. In comparison to laser powder bed processes, arc-based additive manufacturing processes have the additional advantage of an almost unlimited assembly space, higher deposition rates and an improved utilisation factor of raw materials. Disadvantages of wire-based methods are the restricted availability of different types of wire consumables, the fact that the wire feed rate is directly coupled to the heat input and the lack of possibility to create multi-material structures in-situ.Within this work, the 3D Plasma Metal Deposition (3DPMD) method, based on a plasma powder deposition process is introduced. 3DPMD has some special advantages compared to the established plasma powder process and other additive processes. For example, up to four powders, which can differ in terms of material and powder fraction, can be mixed within one layer. This allows a targeted adaption of local properties (microstructure, mechanical properties, wear resistance, porosity, etc.) to the targeted load type and level. The tailored introduction of reinforcement particles, e.g. tungsten or titanium carbides, into the component is a simple example.The study aims to demonstrate the suitability of the 3DPMD for the production of titanium components in layer-by-layer design. Various demonstrators are prepared and analysed. The microstructures, the porosity and the hardness values of the different structures are analysed.In summary, 3DPMD offers the possibility to produce titanium structures with and without reinforcement particles. Using automated routines, it is possible to generate metallic structures directly from the CAD drawings using welding robots. Microstructures and properties are directly related to the process and, therefore, structure-process-property relationships are discussed within this work.
High heat input during welding leads to transformations of the microstructure in the area subjected to welding, mostly resulting in an inhomogeneous microstructure and an overall deterioration of the mechanical properties. To restore these properties, post treatment processes which are typically separated from the welding process are state of the art. The present work focusses on recrystallization phenomena and shows the new methodology, WeldForming, which intends to eliminate subsequent treatment processes. The new inline process combination harnesses the synergies of a welding and a rolling process to ultimately prevent the typical zone formation of the heat affected zone. This is done by stimulating recrystallization and recovery processes. The development of the process is based on numerical simulations. A new aspect is the first time coupling of both processes in a single simulation model. The required material models were generated with the aid of thermophysical simulations. A novel approach is shown for creating a material model for the filler metal G4Si1 with the typical directed solidification microstructure. On the basis of the gained knowledge out of thermomechanical and numerical simulation, a process window was identified and a test setup was developed which gave the functional prove of the WeldForming process.
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