Powder Injection Molding Research Articles

Process Parameters Used in Macro/Micro Powder Injection Molding: An Overview

Powder injection molding (PIM) is a well-known manufacturing technique for the production of complex, net-shaped macro-parts using a broad range of materials and alloys. Eventually, the PIM method has been modified into micro-powder injection molding (μPIM) because of the increasing demand of micro-parts in global market. Now-a-days PIM and μPIM processes are extensively using to fabricate components for electronic, automobile, and biomedical fields. In this paper, the important process parameters that had been used to fabricate defect-free macro and micro-sized parts of different metals, ceramics, and alloys using the above-mentioned techniques have been reviewed. This article is enclosed with a brief discussion on the future research guidelines addressing different aspects related to the two-component macro and micro powder injection molding. This paper could be a worthy source for those investigators who aim to work on PIM and μPIM technology.

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<sub>2</sub> with polyethylene glycol (PEG), polymethyl methacrylate (PMMA) and stearic acid (SA) binders were prepared by PIM process. The average particle size of ZrO<sub>2</sub> powder was 50 nm with pycnometer density of 6.054 g/cm<sup>3</sup>. The ZrO<sub>2</sub> 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<sup>3</sup> 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.

Optimization of the Sintering Parameters for Materials Manufactured by Powder Injection Molding

The properties of sintered and heat-treated steels produced from the Catamold 8740 material by powder injection molding were examined. Parts made of the Catamold 8740 low-alloy mild carbon steel are used in the military, automotive, and other industries where high reliability and resistance to dynamic loads are required. The Catamold 8740 chemical homogeneity was studied as a function of powder injection molding parameters: heating rate, sintering temperature, holding time, and subsequent heat treatment. Microscopic analysis showed that Catamold 8740 was a mechanical mixture of powders in various sizes (carbonyl iron, nickel, Fe–Mo, Fe–Cr, Fe–Si-Mo, Fe–Si). When the heating rate of the Catamold 8740 powder mixture increased from 2 to 5 °C/min, the microstructural heterogeneity caused by uneven compaction decreased and the alloy formation process activated at 900–1340°C. The impact strength of Charpy V-notch test samples changed from 10.39 to 11.52 J/cm2 with higher sintering temperature and heating rate increasing from 2 °C/min (1270°C) to 5 °C/min (1340°C). When holding time increased from 30 to 90 min at a sintering temperature of 1340°C, the material became denser, the pores rounded, and the ferrite matrix homogeneous. However, the impact strength decreased by a factor of 1.4 because of coarser grain sizes and brittle fracture. Heat treatment processes reduced the impact strength after sintering. The results obtained were used to optimize the powder injection molding parameters. The influence of chemical and dimensional inhomogeneity of the starting Catamold 8740 powders and sintering kinetics on the structure and mechanical properties of parts operating under impact loads was established.

Production of Mg-Ca-Zn-Zr-Cu alloy for resorbable compression screw in bone fixation applications

ABSTRACT In this work, biodegradable Mg-Ca-Zn-Zr-Cu alloy specimens were manufactured for temporary implant (compression bone screw or interference screw) applications in the bone fixation applications. Mg-Ca-Zn-Zr-Cu alloy specimens were produced by the metal (powder) injection moulding (MIM/PIM) method. Small and complex parts can be manufactured with the metal (powder) injection moulding (MIM) technique. The metal powder mixtures were mechanically alloyed to prepare the Mg alloys. A mixture consisting of paraffin wax, polyethylene and stearic acid was used as a multi-component polymer binder. Electrochemical corrosion performance of the Mg alloy samples was investigated in the simulated body fluid solution. The experimental findings demonstrated that the electrochemical corrosion resistance of the samples was enhanced with the alloying the Mg. Biodegradation (resorption) performance of the specimens was investigated by using weight change and metal (Mg) ion release measurements. Effect of the alloying elements on the Young’s (elastic) modulus of the alloy was also studied.

Controlling the sintering response in the development of multilayered components produced via powder injection molding route—a review

The development of multilayered components is essential to modern-day technological operations. Several routes to develop these components have emerged, but powder injection molding (PIM) has the benefits of simplicity, non-formation of a third layer, and near-net-shape production. However, PIM presents the challenges of shrinkage mismatch and formation of undesirable phases, which deteriorate the quality and integrity required in multilayered components. The sintering process has been identified as the key step in this route where defects originate; therefore, its parameters (temperature, time, rate, and atmosphere) must be carefully controlled and monitored. This review touches on various processing routes in developing multilayered components, cuts across the achievements made so far in the PIM route majorly in controlling the sintering response of layers, and then sets some guidelines and highlights possible gray areas for future research studies. Some measurement techniques deployed to evaluate shrinkage during sintering, and numerical simulation analyses of PIM processes are also described and analyzed. Thus far, only few mechanical properties have been successfully evaluated in the literature and are discussed in this article.

Comparison of the Crystal Structure and Wear Resistance of Co-Based Alloys with Low Carbon Content Manufactured by Selective Laser Sintering and Powder Injection Molding

Cobalt alloys are widely used in biomedicine, implantology, and dentistry due to their high corrosion resistance and good mechanical properties. The high carbon improves the wear properties, but causes fragility and dangerous cracking of elements during use. The aim of the present work was to analyze and compare the structure and wear resistance of Co-based alloy samples with low carbon content, produced by Selective Laser Sintering (SLS) and Powder Injection Molding (PIM). Structure characterization, mainly with the use of transmission electron microscopy, was applied to investigate the differences in tribological properties. The better resistance to abrasive wear for SLS was explained by the presence of a hard, intermetallic phase, present as precipitates limited in size and evenly distributed in the cobalt matrix. The second factor was the structure of the cobalt matrix, with dominant content of the hexagonal phase. By combining the characteristic features of the matrix and the reinforcing phase, the analyzed material gains an additional advantage, namely a higher resistance to abrasive wear.

Modification of Interfacial Interactions in Ceramic-Polymer Nanocomposites by Grafting: Morphology and Properties for Powder Injection Molding and Additive Manufacturing

The adhesion of the polymer to ceramic nanoparticles is a key aspect in the manufacturing of ceramic parts by additive manufacturing and injection molding, due to poor separation results in separation during processing. The purpose of this research is to investigate, by means of molecular dynamics simulations and experimental methods, the role of improved interfacial interactions by acrylic acid grafting-high density polyethylene on the adhesion to zirconia nanoparticles and on the composite properties. The polymer grafting results in high adhesion to the nanoparticles, increases the nanoparticles dispersion and improves the viscoelastic and mechanical properties required for additive manufacturing and injection molding.

Investigation of functional core-rim composite part production by inserted powder injection moulding

In this study, the use of Cu and Ni interlayers have been investigated for functional core-rim composite part production with WC-Co 9 wt-% feedstock/steel. For this purpose, different experiments have been performed and joining condition, shear strength and microstructure of the intermediate region have been examined. It has been found that AISI 4340 insert/WC-Co have been joined and 85.8 MPa shear strength achieved, but high speed steel insert has not joined. Moreover, it has been determined that better results are obtained with Ni interlayer. Under the same conditions, when the 40 µm Ni interlayer has been used between AISI 4340 core and WC-Co rim, shear strength has been increased approximately twice and has been 162.7 MPa.

Characterization of near-zero pressure powder injection moulding with sacrificial mould by using fingerprint geometries

This paper presents a process chain of powder injection moulding with sacrificial moulds. The mould is fabricated by vat polymerization based additive manufacturing, which enables production of complex metal parts. A special metal feedstock is developed, which allows near-zero injection pressure. The part is ejected together with the polymer mould. After the mould is dissolved, the released part is debinded and sintered. Micro features are printed on the mould surfaces, and the quality of the part is correlated with the replicated features in each process step. In this way the micro features are used as quality indicator, namely, a fingerprint.

Development of a brazing procedure to join W-2Y2O3 and W-1TiC PIM materials to Eurofer

The present work proposes a brazing technique to address both the mechanical and metallurgical requirements of joining two different tungsten powder injection moulding materials (W-2Y2O3 and W-1TiC) with Eurofer steel. The joining procedure uses pure copper as a filler material and the brazing parameters are 1135 °C for 10 min in a high vacuum furnace. Metallurgical evaluation indicates the achievement, in both cases, of 100% metallic continuity at the interface. The brazing temperature is high enough to activate diffusion phenomena at the interface, giving rise to strong adhesion properties. The mechanical properties are evaluated by shear strength tests with values of 163 ± 55 and 162 ± 6 MPa for W-2Y2O3/Eurofer and W-1TiC/Eurofer, respectively. These values are considerably higher than those obtained in previous works using other interlayer materials. The microhardness of these W-base materials is similar to that in the as-received condition, indicating that it was not affected by the brazing process.

The Study of Sintering Behavior of Stainless Steel 17-4PH-Stainless Steel 316L for Two Materials Powders Injection Molding (2C-PIM) Process

Two materials Powder Injection Molding (2C-PIM) is a recently developed method to manufacture functionally graded components. This study is focused on determining the suitability of two materials combined via experimental PIM technique by the sintering and microstructural evaluations. In addition, the shrinkage behavior between the two materials is also observed. The materials in 2C-PIM are said to be compatible with each other in terms of metallurgical bonding and responsive during the sintering process. The materials are stainless steels 17-4PH and 316L with palm stearin and polyethylene as the binders. It has been found that the difference sintering shrinkage for both materials is not significant due to the coefficient thermal expansion (CTE) between the two materials are quite similar. Therefore stainless steels 17-4PH and 316L can be combined successfully via the 2C-PIM technique.

Ceramic Injection Moulding of engineered glass-ceramics: Boosting the rare-earth free photoluminescence

The obtaining of dense ceramic pieces with versatility of size and shape is a much sought-after objective. Powder Injection Moulding (PIM) and Ceramic Injection Moulding (CIM), in particular, is a well-known technology that allows preparing this kind of complex parts with great variety of materials and at large production volume in a cost-efficient way. Usually, this process provides structural materials for mechanical and conforming purposes, but very few works have focused on manufacture functional porcelains. In this work, CIM method is used to process rare-earth free glass-ceramics with photoluminescent properties. The CIM parameters are optimized to obtain dense ceramic parts based on Na-rich plagioclase previously designed. The CIM processed samples show a higher structural disorder as studied by XRD and Raman spectroscopy and variations of the micro-nanostructure, in comparison with conventional ceramic processed samples. Photoluminescent emission studies show an increase of almost one order of magnitude on the UV-blue emission, due to the rise of the structural defect population generated by the CIM process. The CIM process, thus, provides results that boosted the use of rare-earth free materials for luminescence application having complex shapes.

The investigation of production parameters of Ti-6Al-4V component by powder injection molding

Powder injection molding (PIM) is a production method that has advantages of casting and powder metallurgy in the production of parts from different materials, as well as being flexible in the production of complex shaped parts. In this article, experimental studies were carried out for injection and sintering of Ti-6Al-4V feedstock. The results were evaluated by Taguchi method and optimum parameters were determined. Sintering temperature has been determined as the most effective parameter on part quality. It was proven that the suitable set of injection and sintering parameters were as follows: feedstock flow rate of 30 cm3/s, injection pressure of 1100 bar, holding pressure of 70%, injection temperature of 150 °C, mold temperature of 40 °C, sintering temperature of 1250 °C, sintering dwell time of 120 min and sintering heating rate of 3 °C/min.

Improvement of tribological properties of sintered self-lubricating composites produced by surface Mo-enrichment

In powder metallurgy, a high-cost method that is widely used to increase the useful life of the mechanical components is the addition of alloying elements. A less-exploited process is surface enrichment by plasma, where the same result is obtained only on the surface of the component at a rather lower cost. This paper reports on the improvement of the tribological properties of powder injection molding (PIM) self-lubricating composites produced by surface Mo-enrichment. The tribological properties were evaluated in terms of the scuffing resistance, friction coefficient, and wear rate values of enriched and non-enriched specimens, and counter-bodies. Scanning electron microscopy with energy dispersive X-ray spectroscopy and μRaman spectroscopy were used to characterize the wear scars. The results showed that Mo enrichment increased the scuffing resistance by an impressive 2000%, with a 90% decrease in the wear rate of the specimens and counter-bodies. These results were ascribed to several factors, including the microstructural modification, hardness increase, and tribolayer formation.

Warpage of Powder Injection Molded Copper Structure

Powder injection molding (PIM) is an advanced manufacturing technology with advantages including shape complexity, high production rate, and high physical/mechanical properties. However, because PIM has many sub-steps, such as mixing, injection molding, debinding, and sintering, the optimization of each process condition is important to avoid defects including warpage, crack, and blister. In this paper, the warpage, one of the most common defects in PIM, is investigated by using thin square copper structures with lengths of 10 mm and thicknesses of 600 and 190 μm. The warpage of each structure is measured by using a white light interferometric surface profiler. The measured warpage of the structure fabricated by the standard process is 3.771 μm. When the solvent debinding step is absent, the warpage becomes 8.052 μm. Additionally, sensitivity analysis determines that the effect of the thermal debinding step’s heating rate is dominant to warp the structure. Normalized sensitivities of the debinding heating rates are 0.58 for the structure with a thickness of 600 μm and 0.63 for the other structure. Finally, how to optimize the processing condition is outlined.

SS 316L/HA composite via powder injection moulding: Mechanical and physical properties

The bio-active and biological affinity with bony tissue effect of hydroxyapatite (HA) marks as a chosen material for implants application. Uniting HA which has low mechanical properties that limit its application with a higher mechanical property of metallic biomaterial 316L stainless steel (316L) to form a biocomposite have been a solution to produce acceptable mechanical properties for human implant. The 316L/HA biocomposite would have attribute vital to current implant materials, like a low Young’s modulus, high compatibility, and bio-inertness. This study concentrates on investigating the mechanical and physical properties of the 316L/HA biocomposite fabricated by metal injection moulding. The synthesis HA was produced from calcium-Phosphate. While, Polypropylene (PP), Stearin Acid (SA) and primary binder, Paraffin wax (PW) used as a binder system. Different weight of HA (0, 5, 10 and 15 wt. %) ratios to SS 316L/HA were prepared. All samples were sintered at 1350 ºC for 2 hours soaking time. The result shows that 10 wt.% HA biocomposite and above have higher porosity and low mechanical strength. However, 5 wt.% HA biocomposite has a high relative density which 87.95% compared to other additive HA % and hardness 127.10 Hv. The Tensile strength and elongation of 316L/HA biocomposite exhibit decreased as the content of HA wt.% increase which similar properties with the human bone that lower than 130 MPa (tensile strength). Therefore, 5 wt.% HA biocomposite is found to be the most excellent powder ratio for 316L/HA biocomposite regarding mechanical and physical properties and to achieve the mechanical strength of the biocomposite is necessary an amount of HA content in the composite are smaller than 15 wt.%.

Effect of Powder Shape and Size on Rheological, Thermal, and Segregation Properties of Low-Pressure Powder Injection Molding Feedstocks

Optimization of molding parameters at different filling stages requires that the characteristics of low-viscosity feedstocks must be properly known. In this study, the influence of the particle size (3, 7, and 12 μm) and powder morphology (gas- and water-atomized) was quantified using different feedstock formulations based on a 17-4 PH stainless steel powder, all combined with the same binder system. The specific heat capacity, viscosity, and segregation levels were assessed using a differential scanning calorimeter, a rotational rheometer, and a thermogravimetric analyzer, respectively. It was then shown that the feedstock prepared with the gas-atomized powder exhibits a higher specific heat capacity value when compared to a water-atomized powder (i.e., Cp varying from 0.6 to 0.3 J/g K, respectively). It was also shown that the feedstock viscosity profiles and the intensity of segregation both depend significantly on the powder shape and size used in the feedstock formulation. For short processing times (e.g., < 1 min spent in molten state), a feedstock formulated with coarse gas-atomized powder can be considered to be the best candidate for an injection process because its viscosity and segregation potential are relatively low (with a viscosity varying from 0.5 to 2 Pa s, and a volume fraction of powder close to 60 vol.%). Following this, the moldability index was used to predict that coarser water-atomized powder (i.e., 12 versus 7 μm) will not have a significant effect on the molding properties, and can be seen as a potential means of decreasing shrinkage during sintering without impacting the injection properties. For very long processing times, the magnitude of segregation remains insignificant for feedstock formulated with fine powder (i.e., a volume fraction of powder remaining close to 60 vol.%). However, this important gain (i.e., no segregation) comes with a significant increase in viscosity varying from 2 to 10 Pa s, resulting in a decrease in the molding properties.

Optimizing hydride-dehydride Ti-6Al-4V feedstock composition for titanium powder injection moulding

Titanium is used in biomedical applications because it is bio-compatible, has high specific strength and high resistance to corrosion. Powder injection moulding (PIM) produces near-net shaped intricate parts, minimizes secondary operations and makes titanium products more cost effective. Feedstocks with 50–65 vol% powder content were manufactured from commercially available hydride-dehydride titanium alloy powder (HDH Ti-6Al-4V; d10 = 12.8, d50 = 51.8 and d90 = 117.7 μm) and polyvinyl butyral (PVB) based binder. The effect of powder content on mixing torque, feedstock density and viscosity were investigated. Critical powder loadings (CPL) were determined from feedstock density, mixing torque, and viscosity analyses. A new rheological parameter is proposed for predicting CPL based on feedstock flow behaviour. The CPL increased with polyethylene glycol (PEG) content in the binder system. Optimal powder content for HDH Ti-6Al-4V powder was comparable to those reported using small, spherical GA Ti-6Al-4V powder. The HDH Ti-6Al-4V feedstocks exhibited the lowest distribution slope parameter among the published work suggesting it is a cost-effective material for manufacturing parts for biomedical applications.

Effect of pre-calcined ceramic powders at different temperatures on Ni-YSZ anode-supported SOFC cell/stack by low pressure injection molding

Abstract Recently, powder injection molding (PIM) has been exploited in the field of solid oxide fuel cells (SOFCs), especially for fabricating anode supports. The current study employs low pressure injection molding (LPIM) to manufacture near net shape, porous, tubular NiO-yttria stabilized zirconia (YSZ) anode supports for anode-supported SOFCs. The study investigates the effects of pre-calcining temperature of the ceramic powder on the microstructure, porosity and electrochemical performance of the cells in detail. Archimedes tests reveal that the porosity of an unreduced NiO-YSZ anode with 900 °C pre-calcined powder reaches a high of 25.9%, approaching the optimal value of 26%. Meanwhile, the anode prepared under this condition possesses more porous and homogeneous microstructures. At 800 °C, with humidified hydrogen as fuel and ambient air as the oxidant, the single cell with 900 °C pre-calcined powder delivers a maximum power density of 671 mW cm −2 while the cell with raw powder, 555 mW cm −2 , and the cell with 1000 °C pre-calcined powder, 648 mW cm −2 . A four-cell stack is assembled by connecting four single cells in series. The stack could provide a maximum output power of 4.6 W and an open circuit voltage of 3.2 V when fuelled with humidified hydrogen at 800 °C.

Powder Injection Molding of Oxide Ceramic CMC

Ceramic Matrix Composites (CMC) offer improved mechanical properties, especially higher toughness, preferably at elevated temperatures. Fields of application are, for example, highly hot stressed components of aero engines.Processing of Ceramic Matrix Composites by powder injection molding offers attractive economic benefits, however, it represents a considerable challenge. Development of a process chain for the ceramic injection molding of Al2O3 short fiber CMC had started by feedstock preparation and characterization. Fiber content varied between 10 to 50 vol.% whereas for binder a well-examined system from KIT was chosen. The fiber content showed a minor effect on the rheological properties but fiber orientation depended strongly on the apparent shear profile. The sintering behavior was affected as well, i.e. higher densities were achieved.