316L FFF binder development and debinding optimization

Fused Filament Fabrication (FFF) technology is used to create metal parts in this paper. A binder formula is developed for 316L stainless steel powder, composed of polypropylene (PP), styrene ethylene butylene styrene (SEBS) and paraffin wax (PW). The binder is mixed with the 316L stainless steel powder to produce mixture which is then extruded into filament. The optimum binder formula, PP:SEBS:PW=5:2:2, is obtained by orthogonal experiment. After optimization, mixture viscosity is reduced, filament tensile strength is guaranteed, rigidity is improved. The filament can be printed by a desktop FFF printer to obtain green parts. Binder within the green parts can be sufficiently removed by solvent and thermal debinding, and the shape of printed parts can be maintained well. After sintering, shrunken 316L stainless steel parts can be created, some pores distributed inside. With finer metal powder, the relative density of sintered part can be increased to 96%. The research ideas of this paper can provide effective methods for the development and optimization of binder.

Microstructure Evolution of (MgCoNiZnCu)O High Entropy Oxides Using Ceramic Injection Molding

Near net shaping ceramic injection molding process of (MgCoNiZnCu)O high entropy oxides were conducted using commercial precursor oxide powders. Through ball milling, internal mixing, injection molding, solvent and thermal debinding as well as final sintering process, the ceramic products would be obtained with little machining. Compacts prepared are single rock-salt phase based on XRD and EDS Mapping results. Meanwhile, with the increasing of sintering temperature from 900 ℃ to 1050 ℃, particle diffusion rate and densification of samples becomes faster, which finally results relative density and fractured strength of sintered compacts reaching the highest (90.47 % and 77.98 MPa, respectively) in current work. The successfully synthesis of (MgCoNiZnCu)O through ceramic injection molding illustrates this near net shaping process could be a promising route for preparation of high entropy oxides.

Copper additive manufacturing using MIM feedstock: adjustment of printing, debinding, and sintering parameters for processing dense and defectless parts

In the present study, an additive manufacturing process of copper using extrusion 3D printing, solvent and thermal debinding, and sintering was explored. Extrusion 3D printing of metal injection moulding (MIM) feedstock was used to fabricate green body samples. The printing process was performed with optimized parameters to achieve high green density and low surface roughness. To remove water-soluble polymer, the green body was immersed in water for solvent debinding. The interconnected voids formed during solvent debinding were favorable for removing the backbone polymer from the brown body during thermal debinding. Thermal debinding was performed up to 500 °C, and ~ 6.5% total weight loss of the green sample was estimated. Finally, sintering of the thermally debinded samples was performed at 950, 1000, 1030, and 1050°C. The highest sintering temperature provided the highest relative density (94.5%) and isotropic shrinkage. Micro-computed tomography (μCT) examination was performed on green samples and sintered samples, and qualitative and quantitative analysis of the porosity confirmed the benefits of optimized printing conditions for the final microstructure. This work opens up the opportunity for 3D printing and sintering to produce pure copper components with complicated shapes and high density, utilizing raw MIM feedstock as the starting material.

Presintered Titanium-Hydroxyapatite Composite Fabricated via PIM Route

Ti6Al4V-HA composites have been recognized for their potential for biomedical implantation purposes. In the present study, Ti6Al4V-HA composites were fabricated by Powder Injection Molding (PIM) route. Ti6Al4V-HA feedstock at a ratio of 87:13 vol.% was prepared by using a binder system consisting of palm stearin (PS) and polyethylene (PE). The Critical Powder Volume Percentage (CPVP) value for Ti6Al4V-HA was 68 vol.%. Ti6Al4V-HA feedstock was developed at 66 vol.% powder loading. Ti6Al4V-HA feedstock showed pseudoplastic behaviour with a low viscosity and low activation energy of flow and was successfully injected into a tensile bar shape. The debinding process involved a solvent and thermal debinding operation. The debonded parts were sintered at 1300 °C, and the influence of the presintering stage on the physical and mechanical properties of the sintered parts was investigated. It was proven that the presintering stage was able to restrain the transformation of Ti6Al4V into Ti3Al (α2) as well as the decomposition of HA. These are key findings ideas for the designing of sintering parameters, where the decomposition of HA becoming the main problem in the sintering of Ti6Al4V-HA composites at a high temperature. The obtained results also showed that the sintered parts had a porous structure, which looked promising for their use in biomedical implantations. purposes.

Formation of TiO2 Thin Film on Antibacterial Metal Injection Molding Stainless Steel Orthodontic Bracket 17-4 PH Using Physical Vapor Deposition Method

This study aims to equip orthodontic bracket SS 17-4 PH fabricated using metal injection molding with antibacterial properties. This can be achieved by applying TiO2 coating on the surface of brackets using magnetron sputtering PVD method. This method is chosen due to its compatibility to be used on bulk metal and its ability to control thin-film stoichiometry. Samples were prepared using the series of following steps which comprised of metal injection molding, binder elimination with solvent and thermal debinding, sintering in vacuum and argon atmosphere, electropolishing, and magnetron sputtering PVD coatings as the final stage. Negative bias, sputtering power, and partial pressure on vacuum chamber were set as the constant parameters. The atmosphere inside the PVD chamber was controlled using oxygen and argon gases. XRD and SEM observations were carried out to obtain the information on the phase and morphology of the films. Rutile and anatase crystalline structures with 2,27 nm and 9,78 nm crystal size were measured in as-deposited PVD TiO2 respectively. The deposition films were achieved in the range of 3 μm-8 μm.

Injection Molding of 3-3 Hydroxyapatite Composites

The manufacturing of ideal implants requires fabrication processes enabling an adjustment of the shape, porosity and pore sizes to the patient-specific defect. To meet these criteria novel porous hydroxyapatite (HAp) implants were manufactured by combining ceramic injection molding (CIM) with sacrificial templating. Varied amounts (Φ = 0–40 Vol%) of spherical pore formers with a size of 20 µm were added to a HAp-feedstock to generate well-defined porosities of 11.2–45.2 Vol% after thermal debinding and sintering. At pore former contents Φ ≥ 30 Vol% interconnected pore networks were formed. The investigated Young’s modulus and flexural strength decreased with increasing pore former content from 97.3 to 29.1 GPa and 69.0 to 13.0 MPa, agreeing well with a fitted power-law approach. Additionally, interpenetrating HAp/polymer composites were manufactured by infiltrating and afterwards curing of an urethane dimethacrylate-based (UDMA) monomer solution into the porous HAp ceramic preforms. The obtained stiffness (32–46 GPa) and Vickers hardness (1.2–2.1 GPa) of the HAp/UDMA composites were comparable to natural dentin, enamel and other polymer infiltrated ceramic network (PICN) materials. The combination of CIM and sacrificial templating facilitates a near-net shape manufacturing of complex shaped bone and dental implants, whose properties can be directly tailored by the amount, shape and size of the pore formers.