A review on recent developments in binder jetting metal additive manufacturing: materials and process characteristics

Binder Jetting Metal Additive Manufacturing (BJ-MAM), known also as metal 3D-printing, is a powder bed-based additive manufacturing technology. It consists of the deposition of liquid binder droplets to selectively join powder particles to enable the creation of near-net shaped parts, which subsequently are consolidated via sintering process. This technology is known for its capability to process a wide range of different materials and for its orientation towards large volume production series. Binder Jetting has recently been drawing the attention of both the research sphere as well as several industrial sectors. The present review study encompasses the various and most remarkable aspects of BJ-MAM part fabrication. The review covers the material selection and characterisation considerations, followed by the manufacturing process features and the parameter effect on different part properties. It concludes with an overview concerning the most recent case studies with regards to diverse metal alloy developments.This work has been done within the ADDISEND project supported by the ELKARTEK program of the Basque Government [KK-2018/00115]

Hard Metal Production by ERS: Processing Parameter Roles in Final Properties

Cemented carbide is a hard composite material, used widely in a variety of industries. The value of the global tungsten carbide market is expected to grow by 4.4% (compound annual growth rate) from 2017 to 2022. One of the main markets is in metal cutting and wear parts, where small pieces (or inserts), a few grams in weight, are used. Field-assisted sintering technique (FAST) technologies allow for the production of small blanks in a single step from powder, which are near final dimensions. Production cycles are very short. In this paper, one of the FAST processes, the ERS technology, is applied to obtain WC10Co parts. A review of the process variable effects on the final properties of the parts is accomplished. Final properties of a range of conventionally produced inserts are obtained, using 100 MPa compacting pressure, 80 MA/m2 of current density, and processing times of around 800 ms.This research was funded by EU, grant number FoF.NMP.2013-10 608729 (7th Framework Programme) EFFIPRO

Investigation of the Microstructural and Thermoelectric Properties of the (GeTe)0.95(Bi2Te3)0.05 Composition for Thermoelectric Power Generation Applications

In the frame of the current research, the p-type Bi2Te3 doped (GeTe)(0.95)(Bi2Te3)(0.05) alloy composed of hot pressed consolidated submicron structured powder was investigated. The influence of the process parameters (i.e., powder particles size and hot pressing conditions) on both reduction of the lattice thermal conductivity and electronic optimization is described in detail. Very high maximal ZT values of up to similar to 1.6 were obtained and correlated to the microstructural characteristics. Based on the various involved mechanisms, a potential route for further enhancement of the ZT values of the investigated composition is proposed.EC, FP7 PowerDriver Projec

Development of electric resistance sintering process for the fabrication of hard metals: Processing, microstructure and mechanical properties

This work presents the development of the Electrical Resistance Sintering (ERS) process for the fabrication of hard metals. The compositions of the materials produced were WC with 6 and 10 wt% of Co. In addition to the specific characteristics of the technology, the characterization of the produced parts is presented and compared to materials obtained by conventional processes. The parts produced by ERS present densities comparable to the ones obtained by conventional methods. The microstructural comparison shows a considerable grain size reduction in the ERS materials which consequently brings a hardness increase. ERS materials show similar fracture toughness to conventional ones. The very fast sintering allows performing the process without any protective atmosphere, therefore making this process very attractive for the production of materials that need to be sintered under non-oxidising environments. The total duration of the cycle, including heating, holding time and cooling is few seconds. Finally, some considerations about the scale up and possible industrialization of the technology are explained.This work is financially supported by the Seventh Framework Program of the Commission of the European Communities under project EFFIPRO contract no. NMP2-SL-2013-608729

Development of Beta Titanium Alloys by Spark Plasma Sintering

Beta titanium alloys have attracted considerable attention especially for orthopedic implants applications owing to their unique combination of low elastic modulus, superior bio-corrosion resistance and excellent biocompatibility. However, the PM production of these alloys is difficult due to the significant amount of refractory metals (Ta, Mo, Zr, Nb, etc). This work presents a processing route combining mechanical mixing of elemental powders (pre-alloying) and Spark Plasma Sintering in order to obtain fully dense materials with homogeneous microstructure. Two different compositions (TiMo and TiNb) with high amount of alloying elements were developed. The alloys were sintered at temperatures between 1100 and 1250ºC. The phases were evaluated by X-ray diffraction and diffraction of backscattered electrons, appreciating its mechanical properties by micro-hardness and bending tests. A transformation to Beta Titanium is obtained predominantly with a small grain size, and micro-hardness in the order of forged materials.the Spanish Ministry of Economy and Competitiveness through the financial support of the research project MAT2014-53764-C3-1-R and the Generalitat Valenciana through support PROMETEO/2016/040. The European Commission via FEDER funds that have allowed the purchase of equipment for research and Microscopy Service at the Polytechnic University of Valencia

PM Based Titanium Matrix Composites for Aerospace Applications: Processing, Mechanical Properties and Scale Up

The reinforcement of titanium with a hard phase is an efficient way to increase the stiffness and strength of conventional titanium alloys. The high reactivity of titanium is a critical challenge in the processing of Titanium Matrix Composites (TMCs). For this reason, Powder Metallurgy is considered a very promising route for the manufacturing of TMCs. In this work, a master alloy (Ti-TiC) was developed by combustion synthesis. This alloy was further blended with conventional titanium alloy and the final consolidation was performed by Spark Plasma Sintering. In addition to the processing details, microstructural and thermomechanical characterization is presented. Materials obtained present higher Young Modulus and strength than conventional Ti-6Al-4V, with higher thermal conductivity and maintaining similar thermal expansion coefficient (CTE). The good corrosion resistance of the material makes it a candidate for possible applications in aerospace. This work presents also the scale up of the process to obtain aerospace demonstrators.This work was carried out within the frame work of the projects: ‘‘Development and Characterization of Advanced Metal Matrix Composites (Hybrid-MMs)’’) and “Hybrid Titanium Matrix Composites (TMC) for aero engines applications (AIRTMC) both supported by ESA (European Space Agency

Hard Metal Production by ERS: Processing Parameter Roles in Final Properties

Cemented carbide is a hard composite material, used widely in a variety of industries. The value of the global tungsten carbide market is expected to grow by 4.4% (compound annual growth rate) from 2017 to 2022. One of the main markets is in metal cutting and wear parts, where small pieces (or inserts), a few grams in weight, are used. Field-assisted sintering technique (FAST) technologies allow for the production of small blanks in a single step from powder, which are near final dimensions. Production cycles are very short. In this paper, one of the FAST processes, the ERS technology, is applied to obtain WC10Co parts. A review of the process variable effects on the final properties of the parts is accomplished. Final properties of a range of conventionally produced inserts are obtained, using 100 MPa compacting pressure, 80 MA/m2 of current density, and processing times of around 800 ms.This research was funded by EU, grant number FoF. NMP. 2013-10 608729 (7th Framework Programme) EFFIPRO

Simulation of the Electrical Resistance Sintering of Hardmetal Powders

The simulation of the electrical resistance sintering (ERS) of hardmetal powders has been studied. The ERS process can produce a quick consolidation of electrical conductive powders by the simultaneous application of pressure and electrical current. A model of the process has been developed, integrating three actions, namely, thermal, mechanical and electrical, and taking into account the nature of both the powders and the die where powders are placed. The model has been implemented in COMSOL Multiphysics, a finite element commercial program. This paper deals with the model fundamentals and hardmetal particular aspects, such as modelling properties of mixed powders and its thermal behaviour. Other parameters in the model have been tuned to optimally fit the initial experimental data. To check simulation results, measurable parameters have been monitored during experimental tests with WC–6 wt% Co. Once the model was completed and put to work, results are discussed.The authors are grateful to EU for funding this research within the framework of the EU 7th Framework FoF. NMP.2013-10 608729 EFFIPRO Project. The authors also wish to thank the technician Raquel Astacio (University of Seville) for experimental assistanc

Joining of ceramic matrix composites to high temperature ceramics for thermal protection systems

The current work reports a novel approach for the integration of external protective SIC multilayers with ceramic matrix composite (C-f/SiC) with the view of application in aerospace heat protection systems. The integration method is based on diffusion brazing bonding. As a joining agent the MAX-Phase Ti3SiC2, produced by self-propagating high temperature synthesis, has been employed. The pressure applied during the joining process and its effect on the microstructure of the integrated structure is discussed. Microstructural analysis of the resulting joints is conducted using scanning electron microscopy coupled with energy dispersive spectroscopy and X-ray diffraction measurements. Analysis of the joints showed that the bonds are uniform, dense, with few crack vertical to the interface which are not detrimental for the performance of the joints. Ground re-entry tests showed that the joints survive 5 re-entry cycles at 1391 and 1794 degrees C without any detectable damage. (C) 2015 Elsevier Ltd. All rights reserved.European Project "SMARTEES (G.A.) 262749, European Communit