In this paper, silicon carbide fiber-reinforced silicon carbide (SiC f /SiC) composites were fabricated using binder jetting additive manufacturing followed by polymer infiltration and pyrolysis. Spherical SiC powders were produced using milling, spray drying, and thermal plasma treatment, and were characterized using SEM and XRD methods. Irregularly shaped and spherical SiC powders were used to obtain SiC f /SiC blends for the application in binder jetting. The effect of SiC powder shape on densification behavior, microstructure, and mechanical properties of binder jetted SiC f /SiC composites was evaluated. The highest density of 2.52 g/cm 3 was obtained after six polymer infiltration and pyrolysis cycles. The microstructure and mechanical properties of the fabricated SiC f /SiC composites were characterized. Using the spherical SiC powder resulted in higher fracture toughness and hardness, but lower flexural strength compared to the irregularly shaped powder. It was shown that it is feasible to fabricate dense SiC f /SiC composites using binder jetting followed by polymer infiltration and pyrolysis.
In this paper, laser powder-bed fusion (L-PBF) additive manufacturing (AM) with a high-temperature inductive platform preheating was used to fabricate intermetallic TiAl-alloy samples. The gas atomized (GA) and mechanically alloyed plasma spheroidized (MAPS) powders of the Ti-48Al-2Cr-2Nb (at. %) alloy were used as the feedstock material. The effects of L-PBF process parameters—platform preheating temperature—on the relative density, microstructure, phase composition, and mechanical properties of printed material were evaluated. Crack-free intermetallic samples with a high relative density of 99.9% were fabricated using 900 °C preheating temperature. Scanning electron microscopy and X-Ray diffraction analyses revealed a very fine microstructure consisting of lamellar α2/γ colonies, equiaxed γ grains, and retained β phase. Compressive tests showed superior properties of AM material as compared to the conventional TiAl-alloy. However, increased oxygen content was detected in MAPS powder compared to GA powder (~1.1 wt. % and ~0.1 wt. %, respectively), which resulted in lower compressive strength and strain, but higher microhardness compared to the samples produced from GA powder.
In this study, bulk samples of a CrMoNbWV high-entropy alloy (HEA) were obtained for the first time by spark plasma sintering (SPS) of mechanically alloyed (MA) powders at 1200 °C, 1300 °C, and 1400 °C. Microstructure evolution, phase formation as well as wear and corrosion behavior were investigated. The MA powders’ phase composition was found to be represented by body-centered-cubic (BCC) solid solution. The solid solution partially decomposed to Laves phases under the sintering, such as Cr2Nb and (Fe, Cr)Nb, and NbVO4-VO oxides mixture. The temperature increase to 1400 °C led to a grain coarsening of the BCC phase and decreased the Laves phase content accompanied by precipitation at the grain boundaries. The sintered samples showed high hardness and compressive strength (2700–2800 MPa) at room temperature. The wear tests demonstrated excellent results in comparison to conventional wear-resistant composites. The obtained samples also exhibited high corrosion resistance under electrochemical tests in H2SO4 solution. The CrMoNbWV HEA has comparable mechanical and corrosive properties with the WNbMoTaV type HEA, but at the same time has a reduced density: CrMoNbWV—10.55 g/cm3, WNbMoTaV—12.42 g/cm3.
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