Metal Powder Injection Molding Research Articles

An experimental investigation of screw-based material extrusion 3D printing of metallic parts

With the introduction of additive manufacturing (AM) methods, processes with the capability of 3D printing of metal materials were noticed. In general, AM processes with the ability to 3D print metals are more complex and costly in terms of equipment than processes that 3D print other materials (polymers and ceramics). Therefore, the use of 3D printing devices with less complexity and cost, such as extrusion-based 3D printers, for metal printing has attracted the attention of researchers. In this research, an extrusion-based 3D printer, equipped with a direct granule extruder system, was used for 3D printing of the feedstock of the metal powder injection molding (MPIM) process (with 93.7 % by weight of 440 C stainless steel metal powder). The optimal parameters of printing including linear speed (10 mm/s), temperature at the beginning (140 ℃) and end of the barrel (180 ℃), chamber's temperature (60 ℃), and nozzle diameter (0.5 mm) were determined experimentally. The debinding and sintering process was performed on 3D-printed samples. The samples are brittle after the sintering process, in such a way that the failure of the samples occurs by applying a small amount of force to them. According to the scanning electron microscope (SEM) micrograph of the fracture cross-section of the sintered samples, the number of cavities and defects in the samples was negligible and the presence of residual carbon can be seen in the sintered samples. According to the results of X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDAX), the oxidation of iron and chromium elements as well as the presence of residual carbon (7.8 %), are the main factors for the incomplete sintering of the 3D printed samples.

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.

Hybrid Taguchi-Gray Relation Analysis Method for Design of Metal Powder Injection-Molded Artificial Knee Joints with Optimal Powder Concentration and Volume Shrinkage.

Artificial knee joints play a critical role in improving the quality of life of the elderly and those with knee injuries. Such knee joints are fabricated using a composite material consisting of metal alloy particles and polymer resin and are generally produced using the metal powder injection molding (MIM) process. However, if the local powder concentration of the molded product is too low, the mechanical properties and aesthetic appearance of the joint are severely degraded. Similarly, if the product undergoes excessive shrinkage following removal from the mold, the dimensional accuracy will fail to meet the design specifications. Accordingly, the present study applies a hybrid approach based on the Taguchi robust design methodology and gray relation analysis (GRA) theory to determine the optimal MIM processing conditions that simultaneously maximize the powder concentration uniformity while minimizing the volume shrinkage. The feasibility of the proposed approach is demonstrated by means of CAE (Computer Aided Engineering) mold flow simulations. The results show that while the robust Taguchi design method enables the optimal processing parameters that maximize the powder concentration uniformity and minimize the volume shrinkage to be individually determined, the hybrid Taguchi–GRA method enables both quality measures to be optimized simultaneously.

Qualitative and Quantitative Microstructural Analysis of Copper for Sintering Process Optimization in Additive Manufacturing Applications

Abstract This work will present possibilities for the characterization of copper powder green bodies and sintered copper microstructures during pressureless sintering. The introduction of new parameters to microstructural characterization based on qualitative and quantitative microstructural analysis will facilitate the systematic optimization of the sintering process. As a result of the specific evaluation of the microstructure evolution, conventional isothermal sintering could be successfully replaced by multi-step temperature profiles, thus achieving sintering densities of more than 99 % by simultaneously reducing process time. This systematic optimization of the sintering process of Cu through specific microstructural analysis may now be applied to sinter-based manufacturing technologies such as Binder Jetting and Metal Powder Injection Moulding, enabling the manufacture of complex and highly conductive Cu parts for applications in electronics.

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.

On Ultra-compact Gear Manufactured by Micro Metal Powder Injection Molding

On Ultra-compact Gear Manufactured by Micro Metal Powder Injection Molding

Development and improvement of production process of MIM rocker arm

In this article, 17-4PH metal powder was used as raw material to study the effects of the injection position and MIM (metal powder injection molding) thermal debinding temperature on the rocker arm...

Metal Powder Injection Molding Process for Manufacturing Adapter Component

Adapters are a component of the output system in the internally geared hub for a bicycle. Originally, adapter parts were produced by a machining process with low productivity and material usage rate. In this study, the metal powder injection molding (MIM) process has been applied as an alternative manufacturing method to the machining process. Microstructure analysis and mechanical property testing has been conducted in order to select the material for the adapter with changes in the nickel content. The geometrical precision of the adapter is measured by using three-dimensional scanner with various mixing ratios of the powder and the binder. The developed alternative process for the adapter results in increased productivity and material usage rate. Previously, this process was only used for small parts less than 10 mm in diameter. With this development, the MIM process may be used more widely than before.

Quasi-static and high strain rates compressive response of iron and Invar matrix syntactic foams

Abstract The present work is focused on developing iron and FeNi36 Invar matrix syntactic foams and studying their properties under quasi-static and high strain rate compression. The quasi-static compression is conducted at a strain rate of 10−3 s−1. High strain rate testing is performed using a split-Hopkinson pressure bar (SHPB) at strain rates up to 2500 s−1. One of the limitations of the SHPB method is that it does not provide useful results at the intermediate strain rates where the specimens do not fail completely during the test. In the present study, a recently developed repeated testing scheme is applied to obtain results at such intermediate strain rates. Syntactic foams containing 5 and 10 wt.% hollow glass microballoons (GMBs) are synthesized using the metal powder injection molding (MIM) process for this study. The results show that the yield strength decreases with increasing GMB content. The quasi-static yield strengths of 5 and 10 wt.% GMB syntactic iron foams were found to be 14% and 17% lower than that of iron. Similarly, 5 and 10 wt.% GMB syntactic Invar foams had 35% and 51% lower yield strength than Invar alloy. However, weight-related strength was found to increase with GMB content and exceed the respective data of other iron and steel foams. High strain rate testing revealed a weak trend towards yield strength increase with strain rate. However, the indication of strain rate sensitivity is not very strong due to scatter in data. Metallographic analyses conducted on failed specimens showed that the extent of matrix plastic deformation decreased with increasing strain rate. Particle crushing was observed at all strain rates.

Investigation of the mechanical behaviour of AISI 316L stainless steel syntactic foams at different strain-rates

The mechanical behaviour of stainless steel AISI 316L based syntactic foams containing either 40/60vol.% of hollow glass microspheres (S60HS) or 40vol.% of Fillite cenospheres was investigated. In these materials, the hollow particle shells as third phase besides matrix and voids can provide a strengthening effect with the potential of raising mechanical performance above that of conventional, two phase steel foams. Samples were produced by means of metal powder injection moulding (MIM) and subjected to characterization under compressive load, with special attention dedicated to strain-rate sensitivity. Four strain-rate levels were investigated, covering 6 orders of magnitude from 10−3 to 103s−1. For the highest, a Hopkinson Bar apparatus was used. The influence of density on strength was determined for samples containing glass microspheres and described by a power law relationship. The foams mechanical strength was found to increase with strain-rate in accordance with the behaviour observed for the reference material without hollow particles. The data were compared with those obtained in a previous work, in which Fe99.7 matrix syntactic foams containing similar levels of glass microspheres were investigated. The higher strength of the AISI 316L materials is associated with differences in matrix properties. Differences in strain-rate dependence of mechanical properties between both materials can be explained qualitatively based on the fcc (AISI 316L) and bcc (Fe99.7) lattice structure. The introduction of Fillite cenospheres induced a further increase of specific strength. Under quasi-static conditions, samples of this type were found to reach the same yield strength as the reference material despite the reduction in density. The significantly lower strength of glass microsphere based AISI 316L foams can be related to the observed microstructures: due to the high processing temperature (1200°C), glass microspheres are destroyed during sintering, their remainders forming glass inclusions, whereas thermally more stable cenospheres remain intact and can thus stabilize the pores. Finally, an empirical strain-rate sensitive model was adopted to reproduce the experimental data: the fitting procedure used to obtain the model parameters is explained and the influence of the strain-rate discussed. The model allows property prediction for additive content and strain-rate levels further to those evaluated experimentally.

Quasi-static and Dynamic Mechanical Performance of Glass Microsphere- and Cenosphere-based 316L Syntactic Foams

Syntactic foams are produced by adding hollow particles to a solid matrix material. So far, few processes exist that allow manufacturing of such materials using steel matrices. Extremely versatile in this respect are powder metallurgical processes like metal powder injection moulding (MIM), which facilitate usage of different matrix alloys in combination with micro scale fillers. Existing studies on such materials mostly concentrate on quasi-static properties, with Fe99.7 matrices combined with glass microspheres as one exception for which dynamic data has been published. The present work extends the range of matrix materials by summarizing experimental studies on 316L stainless steel foams using glass microspheres as well as cenospheres for the role of introducing porosity. Quasi-static tensile and compressive properties have been evaluated at different density levels – namely 5 and 10wt.-% of microsphere addition - and are contrasted to dynamic performance as determined by means of impact testing and Split Hopkinson Pressure Bar (SHPB) techniques. Failure mechanisms of the materials are discussed in view of the experimental results, evaluations of the foams’ structural characteristics and comparison with the aforementioned existing quasi-static and dynamic data on Fe99.7 syntactic foams. Furthermore, performance is qualitatively and quantitatively compared to other types of 316L stainless steel matrix foams, such as the so-called composite metal foams (CMF) investigated by Rabiei and Vendra (2009).

Production and Properties of 316L Stainless Steel Cellular Materials and Syntactic Foams

316L steel syntactic foams incorporating different mass percentages of soda lime borosilicate glass microspheres (3M™) as porosity‐introducing particles are produced via metal powder injection moulding. Sintering is performed at 1200°C under controlled atmosphere for 1.5, 3, and 6 h. Microstructural features are examined using optical and scanning electron microscopy (SEM) as well as focused ion beam (FIB) preparation and EDX analysis. Response to quasi‐static compressive and tensile loads is studied and interpreted based on structural characterization results. Melting of microspheres is observed, but cavities originally occupied by microspheres are maintained, while glass inclusions form in the surrounding matrix. A qualitative explanation of the underlying process is given. Evaluation of the stress–strain curve reveals a comparatively weak expression of the stress plateau matching the relatively low porosity. Analysis of tensile fracture surfaces indicates a shift of failure initiation sites from spinel type MnCr2O4 phases in the reference material to glass inclusions in foam samples. No major influence of sintering time on structural or mechanical characteristics is identified. Despite the adverse effects of microsphere melting, mechanical performance of 316L syntactic foams matches similar materials having Fe and Fe‐based alloy matrices.

The Viscosity Model of Ti-6Al-4V Feedstocks in Metal Powder Injection Molding

Power Law Model and Cross Model are widely used in Metal Powder Injection Molding computer simulation analysis. The feedstock viscosity data of Ti-6Al-4V is got through field tests, regression analysis is used to calculate the model parameters, which provides the theoretical basis for the application of computer simulation analysis in metal powder injection molding.

Influence of Powder Size on Production Parameters and Properties of Syntactic Invar Foams Produced by Means of Metal Powder Injection Moulding

AbstractThe sintering behavior and the mechanical properties of syntactic foams produced by means of metal‐powder injection moulding depend on the interaction of the metal matrix and the integrated hollow spheres. In order to investigate these mechanisms, Ni‐powder size was varied in the production of FeNi36‐syntactic foams with integrated hollow micro glass spheres. For mechanical characterization tensile tests and RFDA‐measurements were performed as the respective parameters were expected to react most sensitively upon variations of the foam structure.

Markets applications, and financial aspects of global metal powder injection moulding (MIM) technologies

Markets applications, and financial aspects of global metal powder injection moulding (MIM) technologies

Powder injection moulding of metallic and ceramic micro parts

Industrial use of micro components is determined by the availability of efficient manufacturing techniques. While micro injection moulding of plastic is common practice, metal and ceramic powder injection moulding (PIM) still is under development. High-pressure and low-pressure injection moulding methods complement each other ideally, covering the entire spectrum from prototype to large-scale production. With high-pressure PIM, micro gear wheels with diameters <300 μm can be fabricated using LIGA mould inserts. Densities between 97 and 99% of the theoretical values are achieved. Apart from oxide ceramics, metal materials like copper or powder metallurgical steels like 17-4PH or 316L are often applied. Multi-component injection moulding requires less mounting steps and, hence, offers decisive advantages for effective production of interesting material combinations like electrically conductive/insulating or hard/ductile. Studies relating to the fabrication of immobile as well as mobile shaft-wheel components were performed. Other activities focussed on in-mould labelling with foils containing ultra-fine particles to improve surface quality and detail accuracy. Low-pressure injection moulding allows for the manufacture of small series within 1–4 weeks at low cost. However, the process has features which are not compatible with high-pressure PIM. Although use of a low-viscous feedstock is associated with various benefits, low-pressure injection moulding has not met with acceptance in micro moulding.

Fabrication of Micro-Structured Parts by Nano-Imprint Lithography Sacrificial Plastic Mold Insert MIM Using Nano-Sized Copper Powder

This study aims to develop the manufacturing method of micro-structured parts by the metal powder injection molding (MIM) inserted micro-sacrificial plastic molds which were prepared by nano-imprint lithography (NIL) technique. In this process named NIL/μ-SPiMIM, the feedstock composed of nano-sized copper powder and polyacetal-based binder was adequately prepared and molded into polymethylmethacrylate films with fine line-scan structures, and the molded parts were sintered in a reductive gas atmosphere followed by solvent debinding of the films. The behavior in debinding and sintering was investigated by thermo-gravimetric analysis, carbon and oxygen analysis and SEM observation. The effects of sintering temperature on sintered density, shrinkage, and profile accuracy were evaluated systematically. It can be concluded that the manufacturing method named NIL/μ-SPiMIM proposed in this study has great potential to produce precisely 3 dimensional complex metallic parts with fine micro-structures.

S041022 犠牲樹脂型インサート金属粉末射出成形によるインプリント用スタンパーの開発([S04102]粉末成形とその評価(2))

This study aims to develop the manufacturing method of metallic stamper for imprinting with micro structures by metal powder injection molding (MIM). The mold used was prepared by imprinting plastic sheet. In the micro-sacrificial plastic mold insert MIM named as p-SPiMIM process, the feedstock composed of Ni (D50=0.74pm) powder and polyacetal-based binder was filled into polymethylmethacrylate mold with line and space patterns from 47gm wide, 150pm high to 6p.m wide, 19pm high, and it was debinded and sintered in H2 and Ar gas atmosphere. The filling state of feedstock into micro-channels and transcriptional property in sintered parts was evaluated by cross-sectional SEM observation. The experimental results revealed reasonable evidences using submicron Ni powder could sinter at low temperature and accomplished high transcription in narrow cavity mold. It can be concluded that the p-SPiMIM process has potential to mass-produce the stamper for imprinting made of versatile highly-durable metals.

Syntactic Iron Foams with Integrated Microglass Bubbles Produced by Means of Metal Powder Injection Moulding

AbstractSystematic tests for the production of pure iron (99%) foams with integrated microglass bubbles by means of metal powder injection moulding (MIM) have been carried out with variation of the glass bubble contents. Process parameters were optimized and the resulting materials characterized using density measurements, tensile and compression tests, metallographic sections, and scanning electron microscopy. The corrosion behavior of this novel material was characterized using potentiodynamic polarization measurements and immersion tests.

レジスト薄膜インサート金属粉末射出成形によるマイクロ構造体の作製と粉末粒径の影響

The manufacturing method of resist film insert metal powder injection molding (MIM) namely Resist/μ-SpiMIM process has been proposed. The resist film made of PMMA polymer with numerous micro-holes was used as micro sacrificial plastic mold (SP-mold). A novel molding machine which could achieve to mold without pelletizing was also used to produce the green compacts with a high efficiency in experiment by using a small amount of feedstock. The feedstock prepared by pure copper powders with various particle sizes was injection-molded into the SP-mold and the sintered parts with micro-pillar structure were produced after debinding and sintering process. The effects of particle size on density, shape-transcription and surface roughness of those sintered parts were discussed. The decreasing of particle size results in a marked improvements of surface roughness, transcription and dimensional variation of sintered parts.