Browsing by Author "Agote, I."
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Item Fabrication and characterisation of Titanium Matrix Composites obtained using a combination of Self propagating High temperature Synthesis and Spark Plasma Sintering(2016-02-08) Lagos, M. A.; Agote, I.; Atxaga, G.; Adarraga, O.; Pambaguian, L.; EXTREMAT; PRINTEXThis work presents a novel processing method for the fabrication of particle reinforced Titanium Matrix Composites (TMCs). TMCs are a promising alternative to improve the mechanical properties of titanium alloys. In the processing method, the reinforcement (TiC-Ti) was obtained by Self-propagating High-temperature Synthesis (SHS). The composition of the reinforcement was Ti1.3C. An excess of titanium compared to the equiatomic TiC was introduced in the reaction in order to control the size of the reinforcement and to improve the compatibility between reinforcement and matrix. This reinforcement was mixed with Ti-6Al-4V powder and the final consolidation of the TMC was performed by Spark Plasma Sintering (SPS). The microstructure and mechanical characterisation of the TMCs are presented. Comparing tensile properties with conventional Ti-6Al-4V alloys, the materials developed in this work present higher young modulus and tensile strength. In addition, in order to study the possible scale up of SPS process for the production of TMCs, the manufacturing of large samples was studied.Item Fabrication of chromium carbide cermets by electric resistance sintering process: Processing, microstructure and mechanical properties: Processing, microstructure and mechanical properties(2021-02) Lagos, M.A.; Agote, I.; Leizaola, I.; Lopez, D.; Calero, J.A.; EXTREMATChromium carbide-based cermets are suitable for use in abrasive and corrosive environments. This work presents the fabrication of chromium carbide-based cermets by a very fast sintering process: Electric Resistance Sintering. The thermal cycle duration was less than 1 s and without protective atmosphere. Two different compositions were studied: Cr3C2-25NiCr (wt%) and WC-20Cr3C2-7Ni (wt%). Microstructure and crystallographic phases of the initial powders and sintered materials are presented. In addition, hardness and toughness were characterized and compared to conventional materials. One important issue of ERS is the size and homogeneity of the pieces. This work presents the also the fabrication of a mining wear piece and some aspects about scaling up.Item A study of parameter and post-processing effects on surface quality improvement of Binder Jet 3D-printed Invar36 alloy parts(2022-02) Lores, A.; Azurmendi, N.; Agote, I.; Espinosa, E.; García-Blanco, M. B.; EXTREMATBinder Jetting Additive Manufacturing technology, besides its high-productivity manufacturing potential, it also offers a high accuracy fabrication route for less common metal alloys or special purpose applications. In the present work, Binder Jet 3D-printed Invar36 alloy parts’ surface quality improvement is studied. Invar36 is a Fe–Ni alloy which presents near zero coefficient of thermal expansion below its curie temperature (279 °C) and it is widely used for high precision instrumentation in space environment. D90 < 22 µm grade Invar36 powder was used and printing process parameters were optimized following the Taguchi DoE methodology, to reduce sintered parts’ surface roughness. Additional sandblasting and electropolishing operations were performed and part surface roughness was reduced from 5 µm Ra to 1.5 µm Ra. Near surface closed porosity emerged and enlarged during the electropolishing process, leaving a non-homogeneous surface appearance. Consequently, a Hot Isostatic Pressing (HIP) thermal treatment was applied to reduce part overall and near-surface porosity, reaching a relative density of 99.8%. After the sandblasting and electropolishing of HIP-ed parts, surface roughness was further reduced to 1 µm Ra maintaining and homogeneous and clean surface. The results of the study showed that Binder Jet 3D-printed Invar36 parts with low surface roughness can be obtained, getting this process and material closer to future space optics developments.Item Ti3SiC2-Cf composites by spark plasma sintering:: Processing, microstructure and thermo-mechanical properties(2019-08) Lagos, M.A.; Pellegrini, C.; Agote, I.; Azurmendi, N.; Barcena, J.; Parco, M.; Silvestroni, L.; Zoli, L.; Sciti, D.; EXTREMATMAX phases, and particularly Ti3SiC2, are interesting for high temperature applications. The addition of carbon fibers can be used to reduce the density and to modify the properties of the matrix. This work presents the densification and characterization of Ti3SiC2 based composites with short carbon fibers using a fast and simple fabrication approach: dry mixing and densification by Spark Plasma Sintering. Good densification level was obtained below 1400 °C even with a high amount of fibers. The reaction of the fibers with the matrix is limited thanks to the fast processing time and depends on the amount of fibers in the composite. Bending strength at room temperature, between 437 and 120 MPa, is in the range of conventional CMCs with short fibers and according to the resistance of the matrix and the presence of residual porosity. Thermo-mechanical properties of the composites up to 1500 °C are also presented.