Caracterización de CP-Titanio producido mediante inyección aglutinante y pulvimetalurgia convencional

El titanio (Ti) y sus aleaciones se encuentran entre los materiales más utilizados en aplicaciones biomédicas. Además de ser biocompatibles, estos materiales tienen una baja densidad, una alta resistencia a la corrosión y unas propiedades mecánicas notables. Es muy difícil producir piezas con geometría compleja utilizando métodos convencionales de pulvimetalurgia (PM) ya que este método se basa en dar forma a polvos bajo fuerzas uniaxiales utilizando moldes. La Inyección Aglutinante (Binder Jetting) es un tipo de técnica de fabricación aditiva que no necesita moldes para dar forma a los polvos. Este estudio se centra en comparar las propiedades de las piezas porosas de CP-Ti producidas con PM e Inyección Aglutinante. Las piezas se sinterizaron durante 120 min en una atmósfera de argón a 1200 °C. Después de la sinterización, se alcanzaron valores de densidad relativa de aproximadamente el 94% y el 92% en las muestras producidas por PM y con la impresora 3D, respectivamente. También se observó que la muestra producida con una presión de compactación de 25 MPa tiene una dureza de 317 ± 10 HV0.05 y un límite elástico bajo compresión de 928 MPa, mientras que la pieza producida con la impresora 3D tiene una dureza de 238 ± 8 HV0. 05 y un límite elástico bajo compresión de 342 MPa. Aunque la dureza y resistencia de las muestras producidas con la impresora 3D fueron menores que las de PM, sus propiedades son adecuadas para producir implantes que reemplacen las estructuras óseas.

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.

Chloride Diffusion by Build Orientation of Cementitious Material-Based Binder Jetting 3D Printing Mortar

Binder jetting 3D printing (BJ3DP) is used to create geometrical and topology-optimized building structures via architectural geometric design owing to its high degree of freedom in geometry implementation. However, building structures require high mechanical and durability performance. Because of the recent trend of using 3D printing concrete as a structural component in reinforcing bars, its durability with respect to chloride penetration needs to be reviewed. Therefore, in this study, the compressive strength and durability of the chloride diffusion of cement-based 3D-printed output were evaluated. In addition, to confirm the performance difference based on the build orientation, the compressive strength and chloride diffusion were evaluated with respect to the build direction and transverse direction. The experimental results show that the compressive strength was approximately 22.1–26.5% lower in the transverse direction than in the build direction and that the chloride diffusion coefficient was approximately 186.1–407.1% higher in the transverse direction. Consequently, when a structure that requires long-term durability is produced using BJ3DP, it is necessary to examine the design and manufacturing methods in relation to the build orientation in advance.

Binder Jetting and Infiltration of Metal Matrix Nanocomposites

The ability to produce a dense part of Al-based metal matrix nanocomposites using binder jetting followed by infiltration was investigated. A green density above 1.58 g/cm3 was determined to be necessary for spontaneous direct liquid infiltration to commence, and a press-compaction-assisted binder jetting process is needed to achieve this benchmark. A green density of 1.64±0.02 g/cm3 only resulted in a density of 1.65±0.03 g/cm3 by sintering at 1050 °C, which showed that densification is not possible with sintering alone. However, infiltration with Al-6061 produced specimens with a density of 2.74±0.04 g/cm3, which corresponded to a density improvement of 65%. Moreover, the infiltrated specimens had a low open porosity of 2.71±0.95% and a high hardness of 54 HRA. This study suggests that it is feasible to manufacture parts with complex shapes and superior mechanical properties using binder Jetting followed by infiltration.