Powder Injection Molding Process Research Articles

Towards mass production of graphene-reinforced inconel 718 by powder injection moulding

Powder Injection Moulding (PIM) offers a promising avenue for economically producing intricate, graphene-reinforced superalloy parts with complex geometries, overcoming current limitations in their industrialization for engineering applications. The organic binder used in PIM has the potential to be the graphene dispersion media in the superalloy powder saving the need for other processes. However, this addition method needs to be comprehensively evaluated due to the inherent challenges within the PIM process. This study pioneers the utilization of PIM to fabricate Inconel 718 superalloy, incorporating varying levels of reduced graphene oxide (rGO). The effective dispersion of rGO during mixing and its prevalence after debinding and sintering stages have been demonstrated by combining several characterization methods. Graphenic species are identified in all the process stages, though in the sintered microstructure these are commonly accompanied by niobium carbides, which indicates that rGO is partly degraded during the PIM process by reacting with the matrix elements. The encouraging results of this work establish the grounds to produce graphene-reinforced superalloys by PIM and call for further investigation, which can be extended to other metal alloys and ceramics.

Fabrication and characteristics of Li2TiO3 pebbles manufactured by using powder injection molding (PIM) process

The solid type of tritium breeder materials is usually used in a pebble form because of the high packing factor, efficiency of tritium extraction, and advantage of thermal conduction between the structural materials. The breeder pebbles are required a good sphericity and uniform microstructure from the viewpoint of a packing factor and a release of bred tritium. Therefore, in this study, the lithium metatitanate (Li2TiO3) pebbles have been fabricated by powder injection molding process in order to secure a high sphericity of pebbles. In addition, the physical, mechanical, and thermal properties of the pebbles have been investigated. The Li2TiO3 green pebbles have been fabricated by using the powder injection molding process (PIM process). The diameter and sphericity of green pebbles were about 1.000 mm and 1.001, respectively. Then, the green pebbles were sintered at 1000 °C for 3 hr in air atmosphere. The diameter of sintered pebbles is about 0.95 mm. The volume shrinkage ratio was about 16 % during the sintering process. The uniform microstructure with open pores on the inside and outside of the sintered pebbles was observed.

Viscosity Analysis of Copper Aluminium Manganese (CuAlMn) Shape Memory Alloy Mixed with Polyethylene Glycol (Peg), Polymethyl Methacrylate Acrylic (Pmma) and Stearic Acid (Sa) Based Binder

Shape memory alloys (SMAs) are a class of smart materials that have the unusual feature of remembering the initial shape after plastic deformation. SMAs differ from traditional elastic/plastic materials in because of reversible hysteretic thermos mechanical behavior. Copper (Cu) based shape memory alloys are the most promising in terms of practical application due to their inexpensive cost and high recovery force. Powder injection molding (PIM) is well known for the creation of complex components (micro parts) and Copper Aluminium Manganese (CuAlMn) materials are studied through this process. The rheological behavior of the feedstock needs to be determined to avoid any nonhomogeneous mixture between powder and binder that may result in powder and binder separation during the injection molding process. This work focused on the rheological properties of CuAlMn with a binder system of polyethylene glycol (Peg), polymethyl methacrylate acrylic (Pmma) and stearic acid (Sa). The critical powder volume percentage of composite was at 85wt% Cu, 12wt% Al and 3wt% Mn was obtained. Based on such value, the powder loadings used in this work was 58wt% mixed with 73wt% Peg, 12wt% Pmma and 5wt% Sa. A capillary rheometer was employed for the rheological studies where the relationship between shear rate and viscosity was investigated. There were 3 variant temperatures (115℃, 125℃ and 135℃) and 4 loads (40N, 50N, 60N and 70N) applied for the rheology test. The obtained result shows that the overall shear rate and viscosity are within the PIM process recommended range and flow index is below 1. This shows pseudoplastic behavior of the feedstock.

High-capacity Li4Ti5O12-C thick ceramic electrodes manufactured by powder injection moulding

Lithium-ion batteries are the most efficient electrochemical energy storage devices. However, there is still room for improvement in terms of safety and energy density, presently limited by conventional tape-casting electrode processing. In this study, a blend of the anodic material Li4Ti5O12 with 2 wt% carbon black has been processed through powder injection moulding (PIM) yielding, after subsequent debinding and sintering processes, to ultra-thick (>500 µm) ceramic binder-free electrodes. The mixture of Li4Ti5O12 with the thermoplastic binder composed of polypropylene, paraffin wax, and stearic acid is investigated to identify a rheologically suitable feedstock for the PIM process. The resulting disk-type green parts contain 50 vol% of ceramic powder. After removing the binder with solvents and subsequent thermal treatment, the parts are sintered at 900 °C, aiming for a relatively high porosity, i.e., 25.7%. The resulting electrodes show very high areal and volumetric capacities up to 26.0 mA·h·cm−2 and 403 mA·h·cm−3 at C/24, respectively, in a half-cell against lithium metal.

Rheological and mechanical assessment for formulating hybrid feedstock to be used in MIM & FFF

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.

Mass production of superhydrophilic micropatterned copper surfaces using powder injection molding process

Hydrophilic micropatterned copper surfaces are manufactured using a powder injection molding (PIM) process. Copper powder and a wax-polymer-based binder system are utilized to prepare a feedstock. The rheological properties of the feedstock are evaluated to design the PIM process. Polymethylmethacrylate (PMMA) sacrificial mold inserts fabricated by photolithography are used to shape the micropatterns. Both PIM and photolithography processes are suitable for high-volume products; therefore, the micropatterned surfaces can be mass-produced. The wettability of the manufactured surfaces is investigated by measuring the apparent contact angle. The apparent contact angle tends to decrease as the absolute value of the difference in effective surface free energy between the wet and dry states increases. When the absolute value of the difference is equal to or exceeds 150 mJ/m 2 , the surface is fully wetted immediately and exhibits superhydrophilicity. Both high aspect ratio and small gap size are key to achieving superhydrophilicity of the micropatterned surface. • Superhydrophilic micropatterned copper surface is manufactured without any defects. • Rheological analysis of the copper feedstock indicates that it is suitable for PIM. • PMMA sacrificial mold inserts fabricated using photolithography shape micropatterns. • The combined process is suitable for mass production of superhydrophilic surfaces. • Wettability of the micropatterned surface is linked to the dimensions of the pattern.

Analysing Powder Injection Moulding of a Helix Geometry Using Soft Tooling.

Freeform injection moulding is a novel technology for powder injection moulding where a sacrificial 3D printed mould (i.e., a soft tooling) is used as an insert in the injection process. The use of 3D printed moulds enable a higher geometrical design flexibility as compared to the conventional injection moulding process. However, there is still very limited knowledge on how the sacrificial soft tooling material and powder suspension handles the increased geometrical complexity during the process. In this study, a stainless steel powder suspension is injected into a geometrically challenging sacrificial mould (viz. a helix structure) that is produced by vat photopolymerization additive manufacturing. Computed tomography is used to quantify the geometrical precision of the mould both before and after injection. In addition, a new numerical model that considers the suspension feedstock is developed to investigate the powder injection moulding process. The numerical results are found to be in qualitative good agreement with the experimental findings in terms of pinpointing critical areas of the structure, thereby highlighting a new pathway for evaluating sacrificial inserts for powder injection moulding with a high geometrical complexity.

Development of mechanical and visible transparency properties of spark plasma sintered spinel fabricated by powder injection molding of MgAl2O4 nanoparticles

This research aims to investigate the density, hardness, fracture toughness, and infrared and visible transmittance of spark plasma sintered (SPS) spinel discs fabricated through the powder injection molding (PIM) method. These properties were compared with the sample directly SPSed without the PIM process. For this purpose, initially, a feedstock was prepared with 80 wt% spinel nanopowder and 20 wt% binder. The results revealed that the hardness and fracture toughness of the SPSed spinel disc sintered at 1400 °C were greater than those of the spinel sample without PIM treatment. Also, for the PIMed sample and then SPSed sample, the level of infrared and visible transmittance was ~10% greater than for the SPSed spinel nanopowders.

Rheological properties of irregular-shaped titanium-hydroxyapatite bimodal powder composite moulded by powder injection moulding

This paper presents an alternative approach in powder injection moulding (PIM) process by highlighting the advantages of using irregular-shaped and bimodal size powder in Ti6Al4V-HA composite. An investigation on the rheological behaviour Ti6Al4V-HA feedstock at a ratio of 90:10 weight percent was done using spherical and irregular shapes of Ti6Al4V powder particle, together with palm stearin and polyethylene acts as a binder system. Subsequent to the rheological results, the critical powder volume percentage (CPVP) value of the bimodal feedstock improved by 5–8 vol. %. Furthermore, an irregular-shaped Ti6Al4V-HA shows pseudoplastic behaviour and low viscosity with the values of 73–408 Pa.s which is comparable with the spherical-shaped Ti6Al4V-HA (48–305 Pa.s). The injected parts of bimodal irregular-shaped Ti6Al4V-HA also successfully produced without any cracks and distortion with high relative density of 95% after sintering. The result is supported by SEM morphological images which displays micron size porosities that will benefit the sintered part as scaffold for a good osseointegration property with cells. The findings highlight the suitability of irregular-shaped Ti6Al4V-HA during injection moulding as it had outstanding rheological behaviour as good as spherical-shaped Ti6Al4V-HA. Sintered irregular-shaped Ti6Al4V-HA with porous morphological structure, suggest a useful alternative material of irregular morphology of Ti alloy in biomedical industries especially for bone implant application.

Manufacturing of Nanocomposites via Powder Injection Molding: Focusing on Thermal Management Systems—A Review

AbstractThe rapid evolution of electronic and information technology has increased the performance of the electronic processors significantly. Achieving the optimal performance in a smart electronic device poses a serious challenge as the heat generated during operation will reduce the performance of the device which makes thermal management a determinant factor. Powder injection molding (PIM) is an appropriate and relatively new technology used for mass production of small delicate parts with complex shapes and desired properties. One of the latest advances in the PIM process is the production of metal matrix nanocomposites with huge industrial applications, particularly in electronics manufacturing. Manufacturing of efficient complex-shaped nanocomposites, as thermal management components (passive heatsink), could be achieved through the PIM process. On the other hand, what could pose a challenge is the presence of nanoparticles affecting on the different stages of PIM process including feedstock preparation, molding, debinding, and sintering. In this paper, the effect of nanoparticles on different stages of PIM for the production of heatsinks is investigated. Then, the manufacturing of Cu-, Al-, and Mg-based nanocomposites by powder injection molding, as heatsinks, is reviewed followed by investigating the related advantages and limitations.

Soft Ferrite Material by Powder Injection Molding Process for Power Electronics

The current trend toward the rise in the operating frequency in power electronics allows a dramatic miniaturization of power converters but requires reliable passive components. Spinel ferrites could be appropriate magnetic materials for transformers and inductors, within the range 0.5-5 MHz, providing that power core loss, enhanced by the frequency rise, remains low. This work investigates the opportunity to shape magnetic cores by powder injection molding (PIM), while keeping a low power dissipation in components. It paves the way for designing new core geometries incorporating additional functions such as thermal management. A commercial Mn-Zn granulated ferrite powder was used in this study. The densification state of the ferrite feedstock (wax binder system) was investigated after injection and debinding in samples (ring-shaped cores) sintered with different temperatures: 1140 °C/4 h, 1145 °C/4 h, 1150 °C/4 h, 1155 °C/4 h, and 1160 °C/4 h. A Low carbon content (<; 100 ppm) was confirmed by Instrumental Gas Analysis (IGA) and X-ray diffraction (XRD) analysis revealed that the spinel phase formation was fully achieved after sintering. Core losses data (from 100 to 900 kHz at 50 mT) at different temperature (from room to 110 °C) were analyzed by separating the contributions of the hysteresis (P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">h</sub> ~ A.f), eddy current (P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">e</sub> ~ B.f <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ), and residual (P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> ~ C. <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">fn,</sup> with n > 2) losses. The evolution of the total power losses (P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> ) for toroids made by PIM was compared to the ones of samples fabricated by uniaxial compression (UC). It appears that the losses by hysteresis were always lower for PIM than for UC, whereas it was the opposite for eddy current and residual losses. Microstructural analyses showed that open porosity plays an important role in this behavior.

Moldability of Nano Size Zirconia for Powder Injection Molding Process by Using PEG and PMMA Binders

Powder injection molding (PIM) is a well-known manufacturing technique for the production of metal and ceramic near net shapes. Now-a-days, this technology is largely used in electronics, biomedical, aerospace, automotive, defence and telecommunication industries. In this paper, green parts of ZrO&lt;sub&gt;2&lt;/sub&gt; with polyethylene glycol (PEG), polymethyl methacrylate (PMMA) and stearic acid (SA) binders were prepared by PIM process. The average particle size of ZrO&lt;sub&gt;2&lt;/sub&gt; powder was 50 nm with pycnometer density of 6.054 g/cm&lt;sup&gt;3&lt;/sup&gt;. The ZrO&lt;sub&gt;2&lt;/sub&gt; powder was mixed with binder content of 73 wt.% PEG, 25 wt.% PMMA and 2 wt.% SA. The rheological results showed pseudoplastic properties of the feedstock at 140 °C and 160 °C, which was suitable for PIM process. The suitable injection molding parameters for feedstock at 51 vol.% powder loading such as mold temperature, injection temperature, injection pressure and holding time were 60 °C, 160 °C, 10 bar and 8 s, respectively. At the same powder loading, the green part density of 3.60 g/cm&lt;sup&gt;3&lt;/sup&gt; was measured, whereas for the three-point flexural, the measured strength was in the range of 13-15 MPa. For structural analysis, the morphological properties of the powder as well as the surface and the cross-section of the green part was examined.

Manufacturing, high heat flux testing and post mortem analyses of a W-PIM mock-up

Abstract In the framework of the European material development programme for fusion power plants beyond the international thermonuclear experimental reactor (ITER), tungsten (W) is an attractive candidate as plasma facing material for future fusion reactors. The selection of tungsten is owing to its physical properties such as the high melting point of 3420 °C, the high strength and thermal conductivity, the low thermal expansion and low erosion rate. Disadvantages are the low ductility and fracture toughness at room temperature, low oxidation resistance, and the manufacturing by mechanical machining such as milling and turning, because it is extremely cost and time intensive. Powder Injection Molding (PIM) as near-net-shape technology allows the mass production of complex parts, the direct joining of different materials and the development and manufacturing of composite and prototype materials presenting an interesting alternative process route to conventional manufacturing technologies. With its high precision, the PIM process offers the advantage of reduced costs compared to conventional machining. Isotropic materials, good thermal shock resistance, and high shape complexity are typical properties of PIM tungsten. This contribution describes the fabrication of tungsten monoblocks, in particular for applications in divertor components, via PIM. The assembly to a component (mock-up) was done by Hot Radial Pressing (HRP). Furthermore, this component was characterized by High Heat Flux (HHF) tests at GLADIS and at JUDITH 2, and achieved 1300 cycles @ 20 MW/m². Post mortem analyses were performed quantifying and qualifying the occurring damage by metallographic and microscopical means. The crystallographic texture was analysed by EBSD measurements. No change in microstructure during testing was observed.

Effect of sintering on the microstructure and mechanical properties of alloy titanium-wollastonite composite fabricated by powder injection moulding process

Abstract Composite biomaterials are in high demand in the medical field of today. The combination of bioactive wollastonite (WA) glass ceramic with the biocompatibility of alloy titanium (Ti6Al4V) could be a good candidate for implant applications. The rheological properties of Ti6Al4V/WA feedstock show a pseudoplastic behaviour with low activation energy. The feedstock was successfully injected as a green part with no defects. The green part was solvent debound for 6 h in heptane and thermal debound in an argon environment for 1 h. The brown part was successfully sintered at 1300 °C for 3 h with 5 °C/min heating and cooling rates. The average sintered density was 4.12 g/cm3; which is 97.5% from the theoretical density. The highest Young's modulus obtained was 18.10 GPa; which is in the range of human bone strength. EDX analysis shows that by increasing sintering temperature, the level of oxygen decreased. Cell viability test shown an absorbance increased with days increasing indicated that the cellular were proliferated on the composite Ti6Al4V/WA composite which also proved that the composite was non-toxic. This indicates that the Ti6Al4V/WA composite is suitable for bone implant applications.

Fabrication of Micro-Patterned Surface for Pool-boiling Enhancement by Using Powder Injection Molding Process.

In this study, two kinds of copper micro-patterned surfaces with different heights were fabricated by using a powder injection molding (PIM) process. The micro-pattern’s size was 100 μm, and the gap size was 50 μm. The short micro-pattern’s height was 100 μm, and the height of the tall one was 380 μm. A copper powder and wax-polymer-based binder system was used to fabricate the micro-patterned surfaces. The critical heat flux (CHF) and heat transfer coefficient (HTC) during pool-boiling tests were measured with the micro-patterned surfaces and a reference plain copper surface. The CHF of short and tall micro-patterned surfaces were 1434 and 1444 kW/m2, respectively, and the plain copper surface’s CHF was 1191 kW/m2. The HTC of the plain copper surface and the PIM surface with short and tall micro-patterned surfaces were similar in value up to a heat flux 1000 kW/m2. Beyond that value, the plain surface quickly reached its CHF, while the HTC of the short micro-patterned surface achieved higher values than that of the tall micro-patterned surface. At CHF, the maximum values of HTC for the short micro-pattern, tall micro-pattern, and the plain copper surface were 68, 58, and 57 kW/m2 K.

Rheological properties of titanium-hydroxyapatite with powder space holder composite feedstock for powder injection moulding

Metal-ceramic composites such as titanium-hydroxyapatite have been extensively studied as a new generation of implant material in medical application. The powder injection moulding (PIM) process is one the viable processing method in producing the titanium-hydroxyapatite composite which offers extreme geometry part at a lower cost of production. The final powder injection moulding (PIM) product was influenced by the feedstock rheological and thermal properties that related to the binder selection and the critical solids loading. The emphasis of this study was towards the rheological and thermal properties of Ti6Al4V-hydroxyapatite composite feedstock with the powder space holder using a low-density polyethene and palm stearin binder system. The critical solids loading for 90:10 of Ti6Al4V-hydroxyapatite with 20% of the space holder was selected for capillary rheometer tests. The solids loading was obtained at 73 vol.% with optimal solids loading in the range of 2–5% below the critical solids loading which were 68, 69 and 70 vol.%. All feedstocks exhibited shear thinning behaviour, with the shear rate and viscosity values in the range of the PIM feedstock. The work in this study found that the feedstock of 68 vol.% solids loading possessed the best rheological properties with a higher flow behaviour index.

Powder Injection Molding Process in Industrial Fields

Powder Injection Molding Process in Industrial Fields

Nanopowder Effect on Fe Nano/Micro-Bimodal Powder Injection Molding

The nano/micro-bimodal powder injection molding (PIM) process takes advantage of nano-PIM. Most studies of the process were performed with bimodal powder feedstocks containing only small amounts of nanoparticles because they focused on properties of the samples with the optimal contents of nanoparticles. This study presents how nanoparticles in bimodal powder affect the PIM process. Five different feedstocks were prepared with the powders containing nanoparticles from 0 to 100 pct. The result demonstrated that a decrease in solids loading was offset by nanoparticle addition due to the bimodal packing effect. The nanoparticles also increased the difficulty of the debinding process. Sintering was conducted at 1173 K (900 °C), at which the highest sintered density could be obtained, with various isothermal holding times. Unlike the density, the hardness did not reveal any dependence on the holding time due to grain growth. From this study, 25 pct was regarded as the optimal content of the nanoparticles in the bimodal powder for the maximum density and hardness.

Obtaining of Biopolymer from Onion Used as a Binder in Powder Injection Molding Process

The very important strategy in parts processing by powder injection molding (PIM) technology is the use of organic polymeric materials made from raw and auxiliary materials and from renewable natural sources. Using natural polymers to obtain binders for PIM use is of particular interest. The inulin extraction from the onion bulbs has a major alternative in this area.

A simple and systematic scheme implemented in explicit FEM solver for surface tension effects in powder injection moulding process

In order to simulate more accurately the powder injection moulding process, the explicit finite element method solver is extended with the surface tension effect. The evaluation of surface tension takes the notion of pressure boundary method, while a simple and systematic scheme is proposed to fit the finite element method solver for the Laplacian operator. Because of the difference in dimension for filling function and velocity function, the integration of filling function in second derivative is not suitable to be transformed into the boundary integration and the integration of function in lower order derivative. To evaluate conveniently the curvature of filling front, hence the force of surface tension, a simple and systematic scheme is suggested and implemented into the finite element method solver. This specific scheme includes only the vectorial operations in low cost, and is completely systematic without piecemeal operations. Fitness of the proposed method is proved by the numerical examples of filling flow in a small-scaled channel. It shows the considerable effect of surface tension for the problems in micro-scale of sub-millimeter sizes, in which the boundary conditions at front surface are not negligible in powder injection moulding process. The surface tension effect becomes the dominating role for governing the trace and shape of filling front, which can no longer be neglected.