Powder Injection Molding Research Articles

Research on and Application of Feature Recognition and Intelligent Retrieval Method for Multi-Component Alloy Powder Injection Molding Gear Based on Partition Templates

The forming process of multi-alloy gears by metal powder injection molding is tedious, and the current design process mainly depends on the experience of designers, which seriously affects the product development cycle and forming quality. In order to solve the problem of the gear feature expression being missing, which hinders the automatic retrieval of similar parts in the analogical design process, a feature recognition and intelligent retrieval method for a multi-alloy powder injection molding gear based on partition templates is proposed in this paper. The partition templates of the gear are defined, and gear digitization is completed by using the automatic recognition algorithm. Searching for similar gear parts in the knowledge base, designers can analogically design the forming process for new parts according to the mature process of the parts in the knowledge base. The automatic identification and intelligent retrieval system developed according to this method has been implemented in two MIM (metal injection molding) product manufacturing enterprises. Case studies and industrial applications have proved the effectiveness of the system, the efficiency of identification and retrieval has been improved by more than 97%, and the number of mold tests has been reduced by 60%.

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.

Moldability and Solvent Debinding of Hydroxyapatite Micro-Part Processed through Micro-Powder Injection Molding

The development of the micro-powder injection molding (µPIM) process from the powder injection molding (PIM) process has been prompted by the demand of the worldwide market to produce micro-sized components. The need for µPIM-processed components is currently rising across a range of industries, including automotive, aerospace, food, biomedical, electronics, and telecommunications. In the current research work, homogeneous HA feedstock with a powder loading of 57 vol.% was prepared by mixing HA powder particles with palm stearin and low-density polyethylene (LDPE) binders at a mixing temperature of 150 °C for 6 h. Defect-free injection molded or green micro-sized components of HA were produced by employing injection pressure, injection time, mold temperature, and melt temperature of 12 bar, 5 s, 110 °C, and 180 °C, respectively. When mold temperatures less than 110 °C were used, short shot defects were frequently observed in green specimens. After solvent debinding at 60 °C for 50 min, 82.2% of the palm stearin was removed from the green part. No difference in dimension between the solvent debound part and the green part was noticed. An open-pore structure developed in the solvent debound HA microcomponent is helpful for eliminating the insoluble LDPE binder during the thermal debinding phase.

Design of Sustainable Aluminium-Based Feedstocks for Composite Extrusion Modelling (CEM).

Additive manufacturing (AM) has become one of the most promising manufacturing techniques in recent years due to the geometric design freedom that this technology offers. The main objective of this study is to explore Composite Extrusion Modelling (CEM) with aluminium as an alternative processing route for aluminium alloys. This process allows for working with pellets that are deposited directly, layer by layer. The aim of the technique is to obtain aluminium alloy samples for industrial applications with high precision, without defects, and which are processed in an environmentally friendly manner. For this purpose, an initial and preliminary study using powder injection moulding (PIM), necessary for the production of samples, has been carried out. The first challenge was the design of a sustainable aluminium-based feedstock. The powder injection moulding technique was used as a first approach to optimise the properties of the feedstock through a combination of water-soluble polymer, polyethyleneglycol (PEG), and cellulose acetate butyrate (CAB) wich produces low CO2 emissions. To do this, a microstructural characterisation was carried out and the critical solid loading and rheological properties of the feedstocks were studied. Furthermore, the debinding conditions and sintering parameters were adjusted in order to obtain samples with the required density for the following processes and with high geometrical accuracy. In the same way, the printing parameters were optimised for proper material deposition.

On the possibilities of merging additive manufacturing and powder injection molding in the production of metal parts

PurposeThis study aims to enhance merging of additive manufacturing (AM) techniques with powder injection molding (PIM). In this way, the prototypes could be 3D-printed and mass production implemented using PIM. Thus, the surface properties and mechanical performance of parts produced using powder/polymer binder feedstocks [material extrusion (MEX) and PIM] were investigated and compared with powder manufacturing based on direct metal laser sintering (DMLS).Design/methodology/approachPIM parts were manufactured from 17-4PH stainless steel PIM-quality powder and powder intended for powder bed fusion compounded with a recently developed environmentally benign binder. Rheological data obtained at the relevant temperatures were used to set up the process parameters of injection molding. The tensile and yield strengths as well as the strain at break were determined for PIM sintered parts and compared to those produced using MEX and DMLS. Surface properties were evaluated through a 3D scanner and analyzed with advanced statistical tools.FindingsAdvanced statistical analyses of the surface properties showed the proximity between the surfaces created via PIM and MEX. The tensile and yield strengths, as well as the strain at break, suggested that DMLS provides sintered samples with the highest strength and ductility; however, PIM parts made from environmentally benign feedstock may successfully compete with this manufacturing route.Originality/valueThis study addresses the issues connected to the merging of two environmentally efficient processing routes. The literature survey included has shown that there is so far no study comparing AM and PIM techniques systematically on the fixed part shape and dimensions using advanced statistical tools to derive the proximity of the investigated processing routes.

Sinter-based additive manufacturing of hardmetals: Review

Hardmetals, commonly referred to as cemented tungsten carbide (WC) or simply tungsten carbide, is one of the oldest liquid phase sintered, two phase composite, powder metallurgical (PM) product. In fact, this year marks the 100th year since the first hardmetal patent was issued. The classic two-phase composite hardmetal structure typically consists of hard ceramic-like WC particles that are embedded in a softer matrix binder phase primarily consisting of cobalt (Co), sometimes in conjunction with other metals such as nickel and iron, that takes into solution some tungsten and carbon.Various shaping methods have been used to fabricate hardmetals into useful products. Traditional machining to shape hardmetal components was extremely difficult due to the high hardness of these materials (significantly harder than any steels used for cutting). Press and sinter was the process of choice for making relatively simple shapes from hardmetals and is still extensively used. To accommodate some shape complexity, die pressed or cold isostatically pressed “green” parts were machined followed by subsequent sintering to shape hardmetal components. Extrusion using organic polymers was another technique that was adapted to make hardmetal rods and bars. Using the powder injection molding (PIM) process to form more complex shapes from hardmetals was a natural evolution. However, the tooling cost and the typically low volume of parts required for many hardmetal applications was a major barrier. At the turn of the century, there was a rapid growth of the additive manufacturing (AM) sector that is capable of fabricating extremely complex shaped components without the use of any tooling. However, the early AM processes that gained commercial viability were founded on the melt-based techniques, which was generally not conducive to processing of hardmetals. Since 2015, a number of sinter-based AM technologies started to emerge and these technologies were found to be better suited for the processing of hardmetals into complex shapes in an economic manner. This paper will review the developments in the processing of hardmetals using some of the different sinter-based AM techniques.

Optimization of Rheology Parameters for Feedstock by Powder Injection Molding (PIM) Via Taguchi Analysis

The most critical process in the powder injection molding method is determining the powder/binder rate and its properties. The most important feature that distinguishes the powder injection molding method from other powder metallurgy production methods is its advantage in producing high raw density and complex shaped parts. However, providing these advantages includes a multi-parameter process that directly affects the injection molding parameters and the final part's mechanical properties. In addition, the difficulty of experimental studies causes energy, time, and cost losses in determining the powder/binder rate and rheological properties of the feedstock so that the advantages of the method turn into a manageable disadvantage. This study performed rheology studies for three different feedstocks (PW/CW/SA, PW/PE/SA, and PEG8000/PP/SA). In this context, this paper determined the rheological properties of different feedstocks to take advantage of the Taguchi analysis. Flow behavior index, viscosity and optimum loading rates were determined separately for all feedstocks. The results exhibited the injection molding can be done with the determined best (58% steatite+PEG8000/PP/SA) F3 feedstock by volume. Based on it was found that viscosity and melt flow index were not a problem for injection molding in three different feedstocks used in the result, advantages and disadvantages were observed.

Injection Flow Rate Threshold Preventing Atypical In-Cavity Pressure during Low-Pressure Powder Injection Molding

Controlling injection parameters is paramount when it comes to producing high-quality green parts using powder injection molding. This work combines experimental and numerical approaches to study the impact of injection parameters on mold in-cavity pressure and on the overall quality of green parts produced by low-pressure powder injection molding. The properties of two low-viscosity feedstocks (formulated from a water-atomized stainless-steel powder and wax-based binder system) were measured and implemented in an Autodesk Moldflow numerical model to quantify the molding pressures, which were finally validated using experimental real-scale injections. The results confirmed that an increase in mold temperature, an increase in feedstock temperature, and a decrease in solid loading decrease the mold in-cavity pressure, which was correlated with the feedstock viscosity. As a key result, real-scale injections confirmed that a minimum flow rate was required to avoid atypical high in-cavity pressure leading to several visual defects such as weld lines, flow marks, cracks, sinks, and incomplete filling. Due to differences in its thermal transfer properties, this flow rate threshold value decreases as the feedstock solid loading increases. For injection speeds higher than this value, the injection pressure measured experimentally was linearly correlated with the injection flow rate.

Powder loading rate impact on the performances of sintered MnZn ferrites fabricated by powder injection moulding

Powder loading rate impact on the performances of sintered MnZn ferrites fabricated by powder injection moulding

Multifunctional Characteristics of BCTH:0.5% Sm3+ Ceramics Prepared via Hydrothermal Method and Powder Injection Molding

Briefly, 0.005-mol Sm3+-doped (Ba0.85Ca0.15)(Ti0.9Hf0.1)O3 ([(Ba0.85Ca0.15)0.995Sm0.005](Ti0.9Hf0.1)O3, BCTH:0.005Sm3+) lead-free ceramics were prepared via hydrothermal method and powder injection molding using paraffin and oleic acid as binders, and the effects of preparation method and sintering conditions on microstructure, dielectric behavior and optical properties were investigated. XRD Rietveld refinement reveals the coexistence of orthogonal, rhombohedral and tetragonal phases, in which the crystal structure and phase fraction are influenced greatly by sintering temperature and holding time. The ceramics present enhanced relaxor behavior and frequency dispersion phenomenon as compared with those prepared by the solid-state sintering method, and the diffusive index γ value is within 1.421–1.673. The transition mechanism and luminescence performance of BCTH:0.005 Sm3+ were analyzed by Blasse formula, photoluminescence spectrum and fluorescence lifetimes, where emission peaks show slight blueshift, fluorescence decay lifetime becomes shorter, electric multipole interaction dominates the energy transfer mechanism, and the down-conversion luminescence is one-photon absorption process. The CIE chromaticity color coordinate (0.4746, 0.5048), correlated color temperature 3134 K and color purity 93.58% are achieved, which reveals that the BCTH:0.005 Sm3+ ceramics express high quality yellow emission rather than orange-red light of the hydrothermal method synthesized nano-powder, and have potential application in optical field.

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.

Smoothed Particle Hydrodynamics Approach for Simulation of Non-Newtonian Flow of Feedstocks Used in Powder Injection Molding

The present work aims to explore the ability to simulate flow patterns and the velocity field in the powder injection molding (PIM) process using the smoothed particle hydrodynamics (SPH) method. Numerical simulations were performed using the DualSPHysics platform. A feedstock formulated from 17-4 PH stainless steel powder (60 vol. % of powder) and a wax-based binder system was prepared to experimentally obtain its rheological properties that were implemented in DualSPHysics using two different viscosity models. The numerical simulations were calibrated, and then validated with real-scale injections using a laboratory injection press. During the calibration step, the feedstock flow momentum equation in the DualSPHysics code was modified and boundary friction coefficients at different injection rates were adjusted to create a frictional effect. During the validation step, these calibrated conditions were used to simulate the flow behavior into a more complex shape, which was compared with experimental measurements. Using an appropriate boundary friction factor, both the frictional effect of the boundaries and the stability of the numerical solution were taken into account to successfully demonstrate the ability of this meshless SPH method. The flow front length and feedstock velocity obtained in a complex cavity were satisfactorily predicted with relative differences of less than 15%.

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.

Powder Injection Moulded Ti6Al4V-HA Composite for Implants

Powder injection moulding (PIM) is widely used to produce complex shapes of Titanium and its alloys. Ti6Al4V-HA feedstocks at 63, 64 and 66 vol.% were produced by combining a Ti6Al4V-HA powder mixture (90:10 wt.%) with a binder system containing palm stearin (PS) and low-density polyethylene (LDPE). Binder system consisted with 60 wt.% of PS and 40 wt.% of LDPE. All powder loading materials were successfully injection moulded into the shape of a tension bar. Following that, all powder loadings were successfully debound in solvent and thermal methods. Based on SEM observation that 66 vol.% powder loading demonstrated homogenized distribution of powder and binder. Hence, 66 vol.% powder loading was selected for further process sintering at 1300 ºC, and its bending strength was evaluated. Sintered Ti6Al4V-HA with porous structure has Young’s modulus of 11 GPa, within the Young modulus of bone (10 to 30 GPa). The results of this study indicate that sintered Ti6Al4V-HA has potential as an implant material.

Structure and Properties of Ti3AlC2-SiC and Ti3AlC2-TiC Materials Obtained by Powder Injection Molding Technology

Powder injection melting (PIM) and material extrusion additive manufacturing (MEAM) are promising production technologies that allow us to obtain products from modern composite materials. These technologies make it possible to obtain products of complex shape from ceramic composite materials, which is a non-trivial task. A highly filled polymer feedstock is used as a source material in such technologies. In this work, a study of the structures and properties of samples obtained from SiC-Ti3AlC2 and TiC-Ti3AlC2 feedstocks by the PIM method was performed. The main purpose of this work was to study the influence of the powder compositions in feedstocks on the rheological properties and the structures of the obtained samples, as well as to determine the sintering parameters of samples of these compositions. In the future, it is planned to use the received and studied feedstocks in material extrusion additive manufacturing (MEAM). It was found that the investigated compositions had different MFI values depending on the composition. The effect of the sintering parameters on the structure and properties was shown. During the sintering of SiC-Ti3AlC2 ceramics in the temperature range of 1200–1400 °C in a vacuum, the main components of the mixture interacted with the formation of Ti3SiC2 and TiC. For materials of the TiC-Ti3AlC2 composition, partial oxidation of the material and the formation of titanium and aluminum oxides was observed.

Influence of SiC polytypes on the mixed lubrication regime of self-lubricating composites containing in situ generated 2D turbostratic graphite

Fe-based self-lubricating composites, in which SiC particles act as precursors to in situ generated 2D turbostratic graphite as a lubricating phase, were produced via powder injection moulding (PIM). In order to study the precursor influence on the solid lubricant structure and properties, hexagonal (α) and cubic (β) SiC polytypes were used. The composites were tribologically tested in dry and low-viscosity oil-lubricated conditions. Distinct precursors did not lead to significant differences between composites. However, due to the highly disordered graphite-rich tribolayer formation, they do provide lubricity, low friction coefficient, and high wear resistance, even in oil-lubricated conditions.

Effect of powders on aluminum nitride components fabricated by PIM

Powder selection is essential to the success of powder injection molding (PIM). In this study, aluminum nitride (AlN) powder synthesized through carbon-thermal (C-R) reduction and direct nitridation (DN) were used as the raw material. These two kinds of powder were mixed with wax-based binder and the rheological properties of AlN feedstocks were examined. Then the green parts were fabricated by powder injection molding and sintered after solvent and thermal debinding. Finally, the appearance, microstructure and thermal conductivity of sintered AlN were inspected. It was found that the C-R powder has higher critical solid loading (60 vol%) than DN powder (58 vol%). Feedstocks viscosity decreased when the shear rate increased, indicating the presence of non-Newtonian pseudoplastic flow. The C-R powder also has better rheology properties with lower viscosity, higher melt flow rate, higher shear thinning, and higher activation energy. As for the performance after short-time sintering, the thermal conductivity of C-R AlN is 183 W·m−1·k−1 while the value of DN AlN is 130 W·m−1·k−1, and the bending strength of C-R AlN is 363 MPa while that of DN AlN is only 320 MPa.

Characterization of Mechanical Properties and Grain Size of Stainless Steel 316L via Metal Powder Injection Molding

The metal powder injection molding process is completed by mixing a metal powder and a binder, performing an injection molding and degreasing process, and then performing a sintering process for high density. The disadvantage of metal powder injection molding is that defects occurring during the process affect mechanical properties, which are worse in mechanical properties than in products manufactured by cold-rolling. In this study, the mechanical properties and microstructure of stainless steel 316L manufactured by the metal powder injection molding process were analyzed. Mechanical properties such as density, tensile strength, and fatigue life were analyzed. The density was measured using Archimedes' principle, and a relative density of 94.62% was achieved compared to the theoretical density. The tensile strength was approximately 539.42 MPa and the elongation to fracture was approximately 92%. The fatigue test was performed at 80% of maximum tensile strength and a stress ratio of R = 0.1. The fatigue life was found in 55% (297 MPa) of maximum tensile strength that achieved 106 cycles. The microstructure was observed through scanning electron microscope after etching, and as a result, the average grain size was 88.51 μm. Using electron backscatter diffraction, inverse pole figure map, image quality map, and kernel average misorientation map of the specimen were observed in three different areas which were undeformed, uniformly deformed, and deformed. Based on these results, it is expected that research is needed to apply the metal powder injection molding process to the manufacture of agricultural machinery parts with complex shapes.