Powder Injection Molding Research Articles

Surface properties of molds for powder injection molding and their effect on feedstock moldability and mold adhesion

The surface energy of various mold materials for low-pressure powder injection molding was evaluated using values of contact angles (Owens–Wendt method), and correlated with the feedstock moldability and mold adhesion. The surface tension of the binder used to formulate a metallic-based feedstock was also measured in the molten state at a typical injection temperature using the pendant drop technique. Real-scale injection tests were performed into metallic and polymeric mold cavities to assess the feedstock moldability and its adhesion with the mold surfaces that were compared with theoretical predictions obtained from the surface energies values. The results confirmed that the adhesion was significantly affected by the interfacial energy between the mold and the binder—in this case, the metallic mold exhibited low adhesion as compared to the polymeric mold. It was finally demonstrated that the adhesion phenomenon is only related to the surface properties of the mold (i.e., they are not related to the solidification rate)—in this case, a gold-coated polymeric mold produced the moldability of a polymeric mold and the adhesion properties of a metallic mold, which translated into a high moldability potential, with no resulting adhesion of the feedstock with the mold.

Effect of Fe-Cr-B on the Microstructure and Mechanical Properties of a Powder Injection Molding Processed Fe-Cr-B/316L Stainless Steel Matrix Composite

Stainless steel-based composites (SMCs) mixed with 316L stainless steel powder and Fe-Cr-B based M alloys powder ed M) powder were manufactured using the powder injection molding (PIM) process, and their microstructure and mechanical properties were investigated. To examine the effect of M content on the properties of SMCs, the M fraction was controlled to 30 vol.%, 50 vol.%, and 70 vol.%. It was observed that PIM-processed Fe-Cr-B/316L SMCs (30 vol.%, 50 vol.%, 70 vol.%) had γ-austenite and minor α-ferrite as a matrix, and (Cr, Fe)2B was formed as a reinforced phase. In tensile tests at room temperature, the yield strengths of the 30 vol.%, 50 vol.%, 70 vol.% M SMCs were measured to be 519.9 MPa, 574.1 MPa, and 604.8 MPa (peak stress), respectively. From the fracture surface observation results, it was found that the deformation behavior changed from the intergranular fracture of boride to intergranular fracture between the matrix and boride, as the M fraction increased. Based on the above results, the deformation and fracture mechanisms of novel Fe-Cr-B/316L SMCs are also discussed.

Structural features of near equiatomic FeCo-2V semi-hard magnetic alloy prepared by MIM technology

The structural properties of a magnetically semi-hard near equiatomic FeCo-2wt%V (FeCoV) alloy produced by Powder Injection Moulding (PIM) (option by fine metal powder - Metal Injection Moulding (MIM) technology) were investigated in this paper. Starting granulate was prepared by mixing FeCoV powder with a low-viscosity binder. After injection, the green samples were first treated with a solvent and then thermally with the same aim of removing the binder. MIM technology was completed by high-temperature sintering for 3.5 hours at temperatures from 1370 OC to 1460 OC in a hydrogen atmosphere, which provides the necessary magnetic and mechanical characteristics. The influence of sintering temperature was investigated concerning the aspects of the processes of structural transformation by the methods of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The appearance of an intense diffraction peak of the ?'-FeCo phase (crystal structure type B2) was registered for all investigated samples. Structural parameters particle size Dmax, Feret X, and Feret Y exhibit constant increase with increase of sintering temperature.

Research Progress on Powder Injection Molding in Malaysia-A Review

In this era, parts complexity, dimensional accuracy, and cost-effectiveness are one of thebasic requirements of the modern industry. Most of the conventional manufacturingtechniques have failed to fulfill the industry’s needs. Powder injection molding (PIM) startedin the early 70s, which is a combination of powder metallurgy and plastic injection moldingthat fulfills the gaps in conventional manufacturing techniques. In Malaysia, PIM wasintroduced by SIRIM Sdn Bhd Malaysia in late 2000. The latter few universities startedworking on PIM. Among all universities, the Advanced Functional Materials Research(AFM) group at Universiti Teknologi PETRONAS (UTP) started to work in 2008 under thedirection of Prof. F. Ahmad and was decided to target various industries and their latestrequirements. The work completed during the past 11 years has been published in varioushigh-quality international journals, secure intellectual property (IP), i.e., trademarks, patents,a pre-commercialization grant from the government, one commercialization agreement, andsigned a technology licensing agreement. They also worked on carbon Nanotube reinforcedcopper nanocomposite for thermal management and secured two patents. This project wascommercialized for heat sink materials for LED Lights. The group is also working oncontrolling the orientation of fibers in the metal matrix to enhance thermal conductivity.Moreover, grafting graphene on metal oxide for its potential use as a radiation shieldingmaterial is one of the noble works. Currently, the group is working on the fabrication of softmagnetic material with enhanced permeability for potential use in hearing Aids, electricmotors, and several other applications. Besides, bio-medical parts like a dental screw, biomedical material of 316L SS reinforced by nano Titanium and additive manufacturing byusing ultra-fused BASF 316L SS parts made through FDM represent the scope of works inPIM.

Research Progress on Low-Pressure Powder Injection Molding

Powder injection molding (PIM) is a well-known technique to manufacture net-shaped, complicated, macro or micro parts employing a wide range of materials and alloys. Depending on the pressure applied to inject the feedstock, this process can be separated into low-pressure (LPIM) and high-pressure (HPIM) injection molding. Although the LPIM and HPIM processes are theoretically similar, all steps have substantial differences, particularly feedstock preparation, injection, and debinding. After decades of focusing on HPIM, low-viscosity feedstocks with improved flowability have recently been produced utilizing low-molecular-weight polymers for LPIM. It has been proven that LPIM can be used for making parts in low quantities or mass production. Compared to HPIM, which could only be used for the mass production of metallic and ceramic components, LPIM can give an outstanding opportunity to cover applications in low or large batch production rates. Due to the use of low-cost equipment, LPIM also provides several economic benefits. However, establishing an optimal binder system for all powders that should be injected at extremely low pressures (below 1 MPa) is challenging. Therefore, various defects may occur throughout the mixing, injection, debinding, and sintering stages. Since all steps in the process are interrelated, it is important to have a general picture of the whole process which needs a scientific overview. This paper reviews the potential of LPIM and the characteristics of all steps. A complete academic and research background survey on the applications, challenges, and prospects has been indicated. It can be concluded that although many challenges of LPIM have been solved, it could be a proper solution to use this process and materials in developing new applications for technologies such as additive manufacturing and processing of sensitive alloys.

Physical Properties of Sintered Stainless Steel 17-4PH Micro-Part Processed by MicroPowder Injection Molding

Micro-powder injection molding (μPIM) is a modification of powder injection molding (PIM) process and a globally recognized manufacturing process route that can be used largely to produce sophisticated micro-sized components using a wide range of metals and ceramics. The demand of μPIM process is currently increasing in various applications in telecommunication, electronics, aerospace, biomedical, and automotive industries. In this research work, sintering at three different temperatures between 1250 °C and 1350 °C at a heating rate of 10 °C/min with a dwelling period of 3 h on micro-injection molded and debound (solvent and thermal) micro-sized components of stainless steel 17-4PH (SS 17-4PH) was carried out. After the sintering operation, defect-free SS 17-4PH micro-specimens were achieved. The relative density, which is referred to as an important physical property of SS 17-4PH micro-parts, increased substantially from 95.3% to 97.5% when the sintering temperature was enhanced from 1250 °C to 1350 °C. The maximum shrinkage of 12.9% was observed in micro-sized specimens at the sintering temperature of 1350 °C. After the completion of sintering process, the findings revealed that SS 17-4PH micro-parts can be produced successfully on the grounds of μPIM process employing the SS 17-4PH feedstock with powder loading of 69 vol.%.

Processing of tungsten heavy alloy by extrusion-based additive manufacturing

Tungsten heavy alloy (WHA) is a class of liquid phase sintered composite material that consists of predominantly tungsten (typically 90 wt% or more) grains dispersed in a matrix of two or more elements chosen from Fe, Ni, Co, and Cu. Due to its unique combination of properties including high density, strength, hardness, toughness and good corrosion resistance, these alloys have found numerous applications in diverse industries such as counter weights, sporting goods, kinetic energy penetrators, radiation shields, vibration dampening devices, etc. Bound Metal Deposition (BMD) is an additive manufacturing (AM) technology that has its roots in Powder Injection Molding (PIM) and a freeform material extrusion process of fused filament fabrication (FFF). The process is capable of rapid prototyping and low volume serial production of complex shaped parts. This paper reports on the preliminary investigations in the processing of a WHA composition using the BMD process.

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.

Preparation of feedstock containing water-soluble binder for powder injection moulding of silver

Feedstock for powder injection moulding of silver was prepared using water-soluble binder composed of polyethylene glycol (PEG) and polyvinyl butyrol (PVB). Silver powders with particle size in range of 1 μm to 20 μm can be mixed with PEG/PVB binder system to form feedstocks having powder loadings of 42 vol% and 45 vol%. PEG can be removed using water leaching method while PVB can be removed by thermal debinding. Specimens retained their shapes during debinding and after debinding. Components fabricated with relatively higher powder loading resulted in higher density with lower porosity. Density of specimens containing powder loading of 42 vol% and 45 vol% and heated at 700℃ is about 43% and 46% of the theoretical value, respectively. Therefore, it can be further developed for porous materials applications.

Investigation of Sinterability of WC-Co Component Comprising of AISI 4340 Steel Inserts

In this study, sinterability of WC-9% Co component with AISI 4340 steel insert was investigated using Inserted Powder Injection Molding (IPIM) method. Sintering experiments were performed at temperatures of 1200 °C to 1350 °C with dwell times of 120, 240, 360 min. Defects such as gaps, cracks and macro-porosities were observed in specimens, sintered at temperatures of 1200 °C and 1250 °C for all dwell times. It was proved that sintering temperature of 1350 °C was as high as it caused insert to get deformed and melted. As a result, the optimum sintering temperature and dwell time were determined to be 1300 °C and 240 min, respectively, at which the highest hardness, compression strength, and sintered density were obtained without any defects such as cracks or gaps.

Development and Production of Artificial Test Swarf to Examine Wear Behavior of Running Engine Components—Geometrically Derived Designs

Subtractive manufacturing processes are usually accompanied by the occurrence of tiny flakes and swarf, which later on cause severe wear and damage, especially in moving components such as rolling or sliding bearings, pistons, etc. However, up until now, such detrimental effects have hardly been investigated. One reason is the lack of a definition of a typical design of debris particle. Therefore, the main goal of the project described in this paper was to elaborate a draft that defines standardized test particles. It had to be evaluated whether test particles could be adequately reproduced and whether they would reveal significant damage potential. Taking into account future mass fabrication, Micro Powder Injection Molding (MicroPIM) was chosen as a production method. Five different 3D designs of geometrically defined test particles were developed. The maximum size of each design was 1167 mm in green state; however, all samples shrank in size during sintering. Specially tailored feedstocks containing 42CrMo4 steel powders were used and the related molding, debinding and sintering procedures were developed. All particle geometries and related mold inserts were developed using a commercial software routine for the layout of runner systems, gate locations and ejector positions. The damage potential of the test particles was evaluated based on trials using journal bearing and shift valve test rigs. Although only a moderate degree of damage potential could be ascertained up until now, it can be expected that the artificial swarf will enable standardized wear test procedures to be developed.

Material extrusion additive manufacturing of zirconia parts using powder injection molding feedstock compositions

The aim of this study is the evaluation of powder injection molding (PIM) binder compositions for the material extrusion (MEX) additive manufacturing of zirconia parts. Four commercial PIM binder compositions were selected and mixed with 45 vol% of yttria-stabilized zirconia powder. Due to the brittle characteristic of the obtained ceramic feedstocks, a screw based pellet printing head was used for printing dense zirconia structures. To compare 3D printing performance, additionally a commercially available zirconia filament was used in this study. Application of PIM binder compositions was limited either due to phase separation during processing, poor printing performance or delamination during solvent debinding. Only one of the PIM based feedstock compositions could be successfully printed, debound and sintered. A ring-on-ring setup was used to investigate the equibiaxial flexural strength after sintering for both pellet and filament printed disks. For benchmarking, cold isostatic pressed (CIP) ceramic discs were fabricated by commercial, ready-to-press, zirconia powder. The ring-on-ring results showed a low Weibull modulus (3 <m<5) for all samples, regardless of the manufacturing process. Fractography on selected samples demonstrated, that the origins of failures are close to the area of the loading ring which indicates an uneven stress distribution along the contact area between the setup and the sample. The pointwise stress concentration is the reason for the immature failure of the samples and the low Weibull modulus. The characteristic strength and 90% confidence intervals were used to compare the strength of ceramic samples produced via additive manufacturing and CIP. Almost similar mechanical properties were obtained for the CIP pressed (σ0 = 657 MPa) and filament printed (σ0 = 531 MPa) samples. However, a lower strength was obtained by the pellet printed samples based on commercial PIM Binder (σ0 = 203 MPa). Fractography analysis indicated poor fusion of printed layers for the samples produced with PIM binder composition as the main reason for poor mechanical performance.

Powder Injection Molding of Ti-Al-W Nano/Micro Bimodal Powders: Structure, Phase Composition and Oxidation Kinetics

Products from the materials of the Ti-Al system are difficult to manufacture. This often restricts the use of such materials despite their outstanding properties. Some of the promising methods for manufacturing products, which allows working with materials of the Ti-Al system, are powder injection molding (PIM) and material extrusion additive manufacturing (MEAM) technologies. In the present study, powder composites Ti-48Al-4W with different powder size distribution, obtained by the electric explosion of wire (EEW) method, were investigated. The powder was used in PIM technology to produce bulk samples. After polymer debinding, PIM samples were sintered in a vacuum and using hot isostatic pressing (HIP) at the same temperatures and isothermal holding times. The results show the influence of size distribution and sintering method on the structure, phase composition, mechanical properties and oxidation resistance of pre-sintered PIM samples. It is found that both the size distribution and sintering method affect the mechanical properties. The smaller the particle size of the powder in the material, the greater the resistance to oxidation of such samples.

Powder Injection Molding an Alternative Method in the Manufacturing of Parts for Vehicles

Powder injection molding (PIM) is one of the most versatile methods for manufacturing small complex shaped components from metal, ceramic powders for the use in many applications. Interesting applications of PIM include the automotive and aerospace industries. PIM can be used to combine multiple parts into a single part with complex geometry, and parts are lighter since porosity remains in the final part while the fatigue resistance increases. Therefore, it can be said that PIM can help reduce the weight of moving vehicles, which is a major concern from the environmental and economic point of view. One of the main limitations of current PIM technology is the long debinding time, which is one of the steps within the process. This has been partially solved by introducing binder systems that undergo catalytic sublimation. However, current catalytic binders have the main problem of high viscosity. In this study, two ways to decrease the viscosity of PIM feedstock materials with polyoxymethylene were investigated. The first way was to reduce the average molecular weight of the binder and the second one to select a polydisperse particle size distribution with high maximum packing fraction.

Structure and mechanical properties of Fe-10Cu alloy obtained by material extrusion-based additive manufacturing method with bimodal powder

The present study has investigated the microstructure and mechanical characteristics of samples prepared from Fe – 10wt% Cu powder using powder injection molding (PIM) and material extrusion-based additive manufacturing (MEAM) technologies. Bimodal nano-micro powder obtained by the electric explosion of a wire (EEW) technology was used as raw material. The bimodal powder is formed directly during the explosion and does not require a mixing step. This article compares the structure and mechanical properties of samples depending on the manufacturing technology, the debinding time, the sintering temperature, and the gaseous medium in which the sintering is performed. The feedstock for both PIM and MEAM was obtained with a powder content of 93wt% (or 65vol.%). Transmission electron microscopy was used to investigate the structure of copper nano-precipitates. The results show that the most effective way to control the properties of the obtained samples is to change the sintering parameters. All investigated parameters (debinding time, sintering temperature and sintering environment) determines the structure and properties of the material. By changing these parameters, it is possible to achieve the same values of porosity and strength for both PIM and MEAM samples.

Growth inhibiting during ultra-high temperature sintering of injection moulded 17-4 PH stainless steel through the dispersion of ZrO2 particle as a thermal stabiliser

ABSTRACT The present work deals with the metal injection moulding and ultra-high temperature sintering of 17-4 PH powder. Purposefully, 5 mass% ZrO2 particles were dispersed by applying high shear stress during feedstock preparation. Uniformly distributed particles effectively hindered the powder boundary migration and limited their growth during ultra-high sintering temperatures. The achieved thermal stability provided a proper condition for reducing the final porosity to 3% and significantly improved the ultimate strength to 1070 MPa after sintering at 1380°C. Also, the ZrO2 particles acted as facilitators of sliding between solid powders and substantially reduced the required pressure for injecting to 700 Bar. Through introducing such a new approach in the field of powder injection moulding by ZrO2 particles, the amount of anisotropic shrinkage was reduced to 2%.

Time-Dependent Properties of Multimodal Polyoxymethylene based binder for Powder Injection Molding

Powder injection molding (PIM) is one of the most versatile methods for the manufacturing of small complex shaped components from metal, ceramic or cemented carbide powders for the use in many applications. PIM consists of mixing the powder and a polymeric binder, injecting this mixture in a mold, debinding and then sintering. Catalytic debinding of polyoxymethylene (POM) is attractive since it shows high debinding rates and low risk of cracking. This work examines the possibility of using bimodal POM as the main component of the binding agent by studying its time-dependent and thermal properties and comparing them to monomodal POM. Furthermore, possible optimization of the binder formulation was investigated by the addition of short molecular weight polymeric chains (wax) to bimodal POM, as to create a multimodal material. It was observed that the magnitude of the complex viscosity for the commercial bimodal material was more than 2 times lower than for the chemically identical monomodal POM within the investigated frequency range. Viscosity values were observed to drop as the content of wax was increased, without compromising thebinders mechanical properties in solid state. A new formulation of bimodal POM plus 8 wt.% of added wax provided the most appropriate results from investigated combinations. This work has shown how the addition of short polymeric chains in POM influences its time-dependent properties in solid and molten state, which can be an important tool for the optimization of binders designed to be used in PIM technology.

Evaluation of Repetitively Used Feedstock for Powder Injection Molding

Evaluation of Repetitively Used Feedstock for Powder Injection Molding

Real-time Diagnosis of Micro Powder Injection Molding Using Integrated Ultrasonic Sensors

Abstract Real-time diagnostics of ceramic powder injection molding using a commercial micromolding machine was performed using ultrasound. Miniature ultrasonic sensors were integrated onto the mold insert. Melt front, solidification, temperature variation and part detachment of the feedstock inside the mold cavity were observed. It has been demonstrated that ultrasonic velocity in feedstock inside the mold cavity, the ultrasonic contact duration during which the part and mold are in contact, and holding pressure can be used to assist with optimization of injection and cooling parameters to minimize energy consumption and maximize process efficiency.

Microstructure, surface topography and mechanical properties of slip cast and powder injection moulded microspecimens made of zirconia

Abstract Investigations on ceramic microspecimens made of Y2O3- stabilized ZrO2 produced by slip casting or micro powder injection moulding are introduced. During the production of the microspecimens, feedstocks and sintering conditions were varied. Differently moulded specimens were examined with respect to their microstructure and surface topography using light microscopy, scanning electron microscopy (SEM) and confocal white light microscopy. Additionally, the mechanical characteristics were investigated by three-point bending tests using a micro universal testing device. The statistical analysis was realised by means of the Weibull theory and interpreted by the aid of SEM images of fracture surfaces. This research allowed to understand correlations between different feedstocks used, process parameters like the sintering conditions applied and the resulting characteristics as well as material properties of the microspecimens. These results could be used to improve the production process.