Improved green and sintered density of alumina parts fabricated by binder jetting and subsequent slurry infiltration

Additive Manufacturing (AM) of ceramics is a constantly emerging field of interest both in research and in industry. Binder jetting-based AM of ceramics in particular offers the opportunity to produce large ceramic parts with a high wall thickness at a high throughput. One limitation is that it requires flowable powders, which are generally coarse and thus exhibit only limited sintering activity. The resulting low sintered densities impede the commercial binder jetting-based production of dense oxide ceramics. We present an approach to efficiently increase the green density of binder jetted alumina parts by optimized slurry infiltration, which also leads to a significant increase in the sintered density. In a first step, alumina parts were fabricated via binder jetting, using a 20-µm-sized alumina powder, yielding relative green densities of about 47–49%. Initial sintering studies with powder compacts showed that sintering even above 1900 °C is not sufficient to achieve acceptable densification. Therefore, green samples were infiltrated with a highly filled ceramic slurry to fill the remaining pores (about 2–5 µm in size) with smaller particles and thus increase the packing density. Particle volume content (40–50 vol%), particle size (100–180 nm) and the infiltration procedure were adapted for tests on cuboid samples to achieve a high penetration of the green bodies and a high degree of pore filling. In this way, the relative green density could be increased starting from about 47% after binder jetting, to 73.4% after infiltration and drying. After sintering at 1675 °C densities above 90% could be achieved, yielding three-point bending strengths up to 145 MPa. As a conclusion, this approach can be regarded as a promising route for overcoming the drawbacks of the binder jetting process on the way to denser, mechanically more stable sintered alumina parts.

Silicon dioxide dispersed effects on some physical and mechanical properties of Al2Si2O5(OH)4

Kaolin and silica of 50 μm grain size were used in different weight percentage. Four combinations have been selected as green compacted bodies. Different sintering temperatures ranging from (1000 – 1400) °C were used to sintered all the combinations under static air. The sintered density, thermal conductivity compression strength and linear shrinkage were tested after sintering. The common behavior indicated that the improvement with its optimum results was found at the combination (Kaolin 20-SiO2 80) Wt. %, sintered at 1400 °C, for 3 hours under static air.

Sintering Additives Effects on the Microstructure and Electrical Behavior of Yttrium Oxide Ceramic Composites

Ceramics type Yttrium oxide with Silicon carbide. were selected to investigate its sintered density, microstructure and electrical properties, after adding V2O5, of 100 nm grain size. Different weight percentages ranging from (0.01, 0.02, 0.03 and 0.04) were used. Dry milling applied for twelve hours. The pelletized samples were sintered at atmospheric of static air and at sintering temperature 1400 ˚C, for three hours. The crustal structure test shoes the phase which is yttrium silicon carbide Scanning electron microscopy, scan sintered microstructure. Samples after sintering were electrically investigated by measuring its capacitance, dielectric constant and their results showed increasing after added V2O5 particles at the combination Yttrium oxide 80 Wt.% -Silicon carbide 20 Wt.% with 0.04 V2O5 Wt.%.

Sintering Additives Effects on the Microstructure and Electrical Behavior of Yttrium Oxide Ceramic Composites

Ceramics type Yttrium oxide with Silicon carbide. were selected to investigate its sintered density, microstructure and electrical properties, after adding V2O5, of 100 nm grain size. Different weight percentages ranging from (0.01,0.02,0.03 and 0.04) were used. Dry milling applied for twelve hours. The pelletized samples were sintered at atmospheric of static air and at sintering temperature 1400 ˚C, for three hours. The crustal structure test shoes the phase which is yttrium silicon carbide Scanning electron microscopy, scan sintered microstructure. Samples after sintering were electrically investigated by measuring its capacitance, dielectric constant and their results showed increasing after added V2O5 particles at the combination Yttrium oxide 80 Wt.% -Silicon carbide 20 Wt.% with 0.04 V2O5 Wt.%.

Effect of Nano Copper on the Densification of Spark Plasma Sintered W–Cu Composites

In the present work, nano Cu (0, 5, 10, 15, 20, 25 wt.%) was added to W, and W–Cu composites were fabricated using the spark plasma sintering (S.P.S.) technique. The densification, microstructural evolution, tensile strength, micro-hardness, and electrical conductivity of the W–Cu composite samples were evaluated. It was observed that increasing the copper content resulted in increasing the relative sintered density, with the highest being 82.26% in the W75% + Cu25% composite. The XRD phase analysis indicated that there was no evidence of intermetallic phases. The highest ultimate (tensile) strength, micro-hardness, and electrical conductivity obtained was 415 MPa, 341.44 HV0.1, and 28.2% IACS, respectively, for a sample containing 25 wt.% nano-copper. Fractography of the tensile tested samples revealed a mixed-mode of fracture. As anticipated, increasing the nano-copper content in the samples resulted in increased electrical conductivity.

Effect of Thermal Debinding Conditions on the Sintered Density of Low-Pressure Powder Injection Molded Iron Parts

Low-pressure powder injection molding (LPIM) is a cost-effective technology for producing intricate small metal parts at high, medium, and low production volumes in applications which, to date, have involved ceramics or spherical metal powders. Since the use of irregular metal powders represents a promising way to reduce overall production costs, this study aims to investigate the potential of manufacturing powder injection molded parts from irregular commercial iron powders using the LPIM approach. To this end, a low viscosity feedstock was injected into a rectangular mold cavity, thermally wick-debound using three different pre-sintering temperatures, and finally sintered using an identical sintering cycle. During debinding, an increase in pre-sintering temperature from 600 to 850 °C decreased the number of fine particles. This decreased the sintered density from 6.2 to 5.1 g/cm3, increased the average pore size from 9 to 14 μm, and decreased pore circularity from 67 to 59%.

Effects of Sintering Temperature on Densification, Microstructure and Mechanical Properties of Al-Based Alloy by High-Velocity Compaction

This present work investigates the effects of sintering temperature on densification, mechanical properties and microstructure of Al-based alloy pressed by high-velocity compaction. The green samples were heated under the flow of high pure (99.99 wt%) N2. The heating rate was 4 °C/min before 315 °C. For reducing the residual stress, the samples were isothermally held for one h. Then, the specimens were respectively heated at the rate of 10 °C/min to the temperature between 540 °C and 700 °C, held for one h, and then furnace-cooled to the room temperature. Results indicate that when the sintered temperature was 640 °C, both the sintered density and mechanical properties was optimum. Differential Scanning Calorimetry, X-ray diffraction of sintered samples, Scanning Electron Microscopy, Energy Dispersive Spectroscopy, and Transmission Electron Microscope were used to analyse the microstructure and phases.

Effect of in situ formation of tungsten semicarbide on the microstructure and mechanical properties of medium carbon steel composites

Fabrication with the in-situ formation of W2C reinforced medium carbon steel (MCS) MMC’s was attempted using W or WO3 and graphite addition to steel. The P/M route comprising milling, compaction and sintering at 1050 °C and 1120 °C respectively in 90% N2 + 10% H2 atmosphere was adopted. Both SEM and BET studies revealed the particle size to be around 100, 7 and 40 µm for MCS, W and WO3, respectively. A complete conversion of tungsten into tungsten semicarbide (W2C) was noted in XRD for the tungsten additions of ∼6, 9 and 12 wt.% with stoichiometrically balanced C (graphite) addition of 0, 0.2 and 0.4 wt.%. However, WO3 + C addition (balanced as above) revealed the partial conversion of WO3 to W2C. The peaks of Fe3C were observed only for MCS + W + C samples and not for MCS + WO3 + C samples in XRD. In SEM, the WO3 phase appeared porous and partially converted, whereas, W2C phase was dense. Sintered density improved for the addition of W, whereas it monotonically reduced for WO3 addition to MCS + C samples. Higher hardness, compressive strength, and wear resistance was noted for W addition than WO3 to MCS+C samples.