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- Optimisation of nanocrystalline size of powder coatings for μMIMPublication . Farinha, A. R.; Cavaleiro, A. J.; Ferreira, T. J.; Barreiros, F. M.; Vieira, M. T.; Barrière, T.; Gelin, J. C.MIM must be optimised concerning 4S powders characteristics: particle size (1S), particle size distribution (2S), shape (3S) and surface (4S). These aspects have particular relevance in net shape processes of micro manufacturing (μMIM), particularly during sintering. Tailoring the surface powders can contribute to a quality improvement of micro parts. The modification of the surface properties of the stainless steel (SS) particles by coating them with a nanometric thin film of a similar material can modify the sintering behaviour of powders. The study of the effect on sintering parameters and microstructure of nanocoatings with similar chemical composition of 316 L SS powders where they are deposited reveals a significant improvement concerning reactivity, porosity and mechanical properties.
- DMLS technology for automotive toolingPublication . Leal, R.; Barreiros, Fatima; Alves, M.L.; Romeiro, F.; Vasco, J.; Santos, M.; Marto, C.The automotive industry is challenged every day, with companies competing and developing new models and facelifts in short term, requiring new tools or tool reshaping. Concerning the current world economic scenario, decreasing time-for-tooling becomes as important as decreasing time-to-market. Such scenario opens up the horizons for new manufacturing approaches like additive manufacturing. In this case-study, additive manufacturing is applied for tooling up a stamping process for the production of body panels for the automotive industry. This approach enables the manufacturing of stamping tool inserts with similar high performance alloy steel as in conventional tooling, although, without any loss of tool properties and saving a significant part of the tool manufacturing time. The evaluation of the tool performance and tool life estimation was carried out based on three point bending fatigue tests using specimens manufactured by the same additive process and using the same powder material. From these data, it was possible to establish realistic scenarios for the use of additive tooling and to evaluate its feasibility on the automotive industry.
- Binder system for fused deposition of metalsPublication . Cruz, N.; Santos, L.; Vasco, Joel; Barreiros, F. M.Fused Deposition of Metals (FDMe) is a technique developed to produce metallic components, based on the extrusion of metal/binder filaments to form layer by layer three dimensional objects. Filament materials must contain a high content of metallic powder to prevent shrinkage on thermal treatments like debinding and sintering, without compromising adequate rheological properties during the extrusion process. This research aims developing an FDMe system using metal/binder feedstocks in pellet/granule instead of filaments. The present work is focused on establishing a suitable binder system for fused deposition of carbonyl iron feedstocks. Binder systems based on Polyethylene Wax (PEW) or Paraffin Wax (PW), Polyethylene Glycol (PEG) and Polypropylene (PP) were investigated concerning their thermal and rheological properties. The rheological data showed that the binder systems containing PW presents lower viscosity than those having PEW. Thus, a binder system based on the former component was selected to assure appropriate rheological properties of carbonyl iron feedstocks with high content of solids for FDMe.