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Addressing large bone segmental defects remains a profound challenge in orthopaedic surgery, demanding graft designs that mirror patient-specific defects while ensuring vascularization, osteoconduction, and structural integrity. Conventional approaches fall short in achieving this level of customization and functionality. This work leverages fuse filament fabrication (FFF) to fabricate innovative yttria stabilize zirconia graft designs that combine several strategies to tackle these multifaceted challenges. Graft designs ingeniously incorporate dense and porous structures mimicking the intricate architecture of natural bone for improved structural integrity and different ridges and protrusions to enhance the fixation. Additionally, these grafts undergo infiltration with PCL/PVA/AgNPs composite polymers, enriching biocompatibility, structural integrity, and antibacterial properties, fostering conducive conditions for optimal bone growth. Attaining printable filaments with YSZ powders below 50 nm and loads reaching 50 vol% marks a pioneering advancement in bone graft fabrication via Fused Filament Fabrication (FFF). This enabled high densification and low grain size at reduced sintering temperatures, imperative to achieve high mechanical performance. The biodegradation capacity of biopolymers in PBS and their role in the mechanical behaviour of grafts have been assessed, demonstrating the beneficial potential of the multicomponent graft proposed reaching strength values of 90–105 MPa.

In advanced powder metallurgy technologies such as metal injection molding (MIM) and material extrusion technology (MEX), the intricate synergy between binder components and metallic powders within feedstocks is predominant, dictating the technological boundaries of metal’s complexity, size, and thickness. This work suggests unique binder constituents (polymers, surfactants and melamine), aiming to boost the debinding efficacy and solid loading while ensuring processability. The interactions and role of melamine by thermal and rheological studies are detailed, spotlighting how, unlike traditional binder systems, the pioneering feedstock introduces beneficial modifications to storage modulus (G′) and loss tangent (tan δ), alongside a lubricating effect on metallic mixtures. This study highlights the potential of melamine to facilitate a more efficient debinding process, with superior formaldehyde management and environmental control. Through this material-centric lens, we offer new pathways to navigate the complexities of MIM and MEX, advancing towards technological enhancement and environmental protection.

Processes involving additive manufacturing (AM) and Powder Injection Moulding (PIM) in industry show great potential in producing parts with complex shapes, covering both short series of customed components and high production volumes. A deep study into the fundamentals of the material flow behaviour according to both processing methods requirements, not previously described, is carried out and the synergy of PIM and AM based on Fused Filament Fabrication (FFF) is confirmed. The significance of having a robust material, defined as “hybrid feedstock”, carefully designed to enable the FFF and PIM process, including the debinding and sintering stages, is discussed. The mechanical properties of the 17-4 PH filaments, such as shear strength and maximum force, are analysed, and it is concluded that the choice of an appropriate binder system is crucial for achievement optimal performance during the printing process. The rheological properties of the materials (fluidity and shear thinning behaviour) are also examined and the importance of considering printing speed and temperature to control nozzle pressure and ensure successful printing is emphasized. Furthermore, the mechanical properties of the filaments with different metallic powder loadings are discussed, The need to stablish limits for material suitability in terms of shear stress and activation energy is also mentioned. Overall, the scientific discussion addresses various relevant aspects related to the mechanical and rheological properties of the materials used in 3D printing of metals using FFF technology. Conclusions based on experimental results are provided and key parameters to consider for successful printed parts are highlighted.

Ceramic Injection Moulding (CIM) is an advanced powder processing technology launched three decades ago which has become a growing attractive alternative for new technical applications, such as thermal management and wireless charging. Porcelain-type ceramics can allow the introduction of new feedstocks into the CIM market at a competitive cost, in comparison with the conventional alumina and zirconia feedstocks. During the CIM manufacturing process, several factors related to the starting powder characteristics have an influence on the quality and properties of the final components, such as the mixing behaviour and the feedstock flow properties, as well as injection, debinding and sintering parameters. In this work, the viability of three porcelain-based powders to successfully achieve injectable mixtures for CIM is described. The mixing behaviour and the feedstocks flow behaviour as a function of its solids loading is evaluated. In this way, the ideal attributes for a CIM porcelain powder are discussed, studying the first process stages through to the production of a sintered component by injection moulding. Finally, density, hardness, bending strength and microstructural properties of the selected porcelain are investigated and a cost-efficient ceramic feedstock is suggested for aesthetic and electrical applications. Resumen: El moldeo por inyección de cerámica (en inglés, Ceramic Injection Moulding [CIM]) es una tecnología avanzada de conformado de polvos establecida hace tres décadas que recientemente se ha convertido en una atractiva alternativa para nuevas aplicaciones avanzadas, como la gestión térmica y la recarga inalámbrica de dispositivos. Las cerámicas de tipo porcelana permiten la introducción de nuevos feedstocks en el mercado CIM a precios más bajos en comparación con los tradicionales de alúmina y zircona. Existen varios factores que influyen en la calidad y las propiedades de los componentes finales en el procesado CIM y que están relacionados con las características del polvo de partida, como son el comportamiento durante el mezclado y la fluidez del feedstock, así como los parámetros de inyección, eliminación y sinterización. En este trabajo se describe la viabilidad de tres porcelanas para obtener mezclas inyectables que puedan procesarse con éxito mediante CIM. Se muestra la estabilización del par de torsión durante el proceso de mezclado, así como la fluidez de los diferentes feedstocks en función de la carga cerámica. Asimismo, se discuten las cualidades que idealmente se buscan en un polvo para ser procesados mediante CIM. Finalmente, se muestran los resultados obtenidos de densidad, propiedades microestructurales y propiedades mecánicas (dureza y resistencia a la flexión) de la porcelana seleccionada, y se demuestra que la mezcla inyectable diseñada a precio competitivo puede utilizarse para aplicaciones estéticas y eléctricas en futuros trabajos.

Additive manufacturing (AM) alternative technologies, including Fused Filament Fabrication (FFF), offer the possibility to produce both prototypes and low-volume production metallic components. This is the first time that AISI M2 high-speed steel powder is processed by FFF, achieving near full density in a complementary way to Powder Injection moulding (PIM), yet reducing the investment cost and the lead time. A completely optimized FFF process is presented: from the design of a printable highly filled metallic filament that can be fed into conventional 3D printers, to high-quality green parts that are properly debound and sintered. The final specimens (99.6% densified) are thermally treated (one quenching and two tempering) and, then, evaluated in terms of scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis and mechanical characterization (hardness and wear resistance). The effect of the processing technology and the heat treatments are discussed, validating the feasibility of FFF to develop customized high-speed tools with superb performance at a competitive cost.

Soft magnetic materials are characterized by achieving a high magnetic induction value in the presence of a small magnetic field. Common applications of these materials, such as transformers or sensors, are in constant evolution and new requirements are becoming more demanding. Nickel and its alloys are employed as smart materials taking advantage of their superior magnetoelastic properties. A metal injection molding (MIM) technique provides high-quality complex-shaped parts with a good density and controlled impurity levels, which are necessary for these applications, by carefully adjusting the sintering stage. Previous investigations have established a sintering cycle for pure nickel consisting of 1325 ∘C for 12 h within an N2-5%H2 atmosphere. Nevertheless, microstructural, mechanical and magnetoelastic responses can still be greatly enhanced. In this context, the effects of hot isostatic pressing (HIP), and sintering atmosphere have been investigated. The application of an adequate HIP treatment leads to significant improvements in comparison to the reference sintering process. It achieves almost complete densification while increasing field-dependent elastic modulus from 8.1% up to 9.6%. Additionally, the sintering atmosphere has been proven to be a key factor in reducing impurities and hence facilitating magnetic domain motion. Three different atmospheres have been studied: N2-5%H2 (with a higher gas flow), N2-10%H2-0.1%CH4 and low vacuum. Minimum carbon contents have been registered using more reducing atmospheres (N2-5%H2 and N2-10%H2-0.1%CH4) which has led to values of field-dependent elastic modulus higher than 10%. This value is 2.5 times higher than that obtained when nickel parts are processed via conventional techniques. Moreover, although minimizing carbon content has been shown to be easier and more beneficial than achieving complete densification, both strategies could be used in combination to improve and maximize magnetoelastic performance.