Powder Injection Molding Research Articles

Effects of Binder and Processing Parameters on Processability of Porous Ti/HA Composite through Powder Injection Molding

Powder injection molding (PIM) process is suitable for both metal and ceramic materials to produce parts with high volume and accuracy at low cost. In this research work, 90wt. % of Ti6Al4V was dry mixed with 10wt. % of Hydroxyapatite (HA). The resultant mixture was further mixed with different space holders in weight ratio 8:2. The feedstock was prepared by mixing the final mixed powder with PEG and PW based binder systems. The dumbbell shape parts were produced using DSM Xplore injection molding machine. The molded samples were debound into two stages i.e solvent extraction followed by thermal debinding. The debinding parameters were optimized for different binder with space holders. The major binders’ paraffin wax (PW) extracted in haptane and PEG in water immersion at temperatures of 60 °C and 50 °C for 5 hrs respectively. The thermal de-binding was performed successfully at 500 °C by varying the heating rate from 3 °C/min-5 °C/min with holding time 1hr in argon atmosphere followed by the sintering in vacuum. During molding short shot defects and cracks were observed while during debinding, collection of binder, swelling and holes were noted. These types of defects may be due to space holder, improper binder, heating rate, temperature and dwell time at each processing step. The sintered test specimens were analyzed for porosity and microstructure. The results showed that the PEG based binder system with NaCl space holder is more effective to produce porous Ti/HA composite through PIM. Porous Ti/HA composite showed interconnected pores with average size of 90µm.

Influence of binder system and temperature on rheological properties of water atomized 316L powder injection moulding feedstocks

In order to obtain a proper powder injection molding the rheological behavior of feedstocks should be known. To determine the binder effect on the rheological behavior of 316L stainless steel powders feedstock two different feedstock were prepared. In the current experiments water atomized 316L stainless steel powders (-20 µm) were used. Two types of binders, one of which is mainly paraffin wax can be dissolved in heptane and the other Polietilenglikol (PEG) based and can be dissolved in water, were used. Polypropylene was used as binder and steric acid was used as lubricant for both binder systems as skeleton binder. Dry binder system were mixed for 30 min in a three dimensional Turbola. Capillary rheometer was used to characterize the rheological properties of feed stocks at 150-200 °C and a pressures of 0.165-2.069 MPa. Powder loading capacity of PEG and PW based feed stocks were found to be %55 and %61 respectively. The lowest viscosity of PEG and PW based feed stocks were found to be 304.707 Pa.s and 48.857 Pa.s respectively. Keywords: PIM, Binder, Rheological properties

Development and identification of rheological model adapted for Powder Injection Moulding

An Inconel based feedstock for manufacturing super alloy components by powder injection moulding is introduced. The relationship between the rheological properties and different parameters of the feedstock is investigated, based on a prescribed model. The method to determine the parameters of the rheological model for powder injection moulding is presented, including the important thermal effect.

Powder metallurgical processing of iron for biodegradable medical implants: Physical and mechanical

Event Abstract Back to Event Powder metallurgical processing of iron for biodegradable medical implants: Physical and mechanical Vinicius Martins1, 2, André C. Tavares1, 2, Lirio Schaeffer2 and Diego Wermuth2 1 Instituto Federal Sul-rio-grandense - IFSul, Mecânica, Brazil 2 Universidade federal do Rio grande do Sul - UFRGS, Metalurgica, Brazil During the last two decades, significant advances have been made in the development of biocompatible and biodegradable materials for medical applications. The powders were analyzed and made test pieces were after analyzed its physical properties. It built up an array to conventional powder metallurgy, compliance with the process parameters as: compression pressure, atmosphere and time sintering. The production by powder metallurgy given to components unique features, as controlled porosity, which differs from Traditional manufacturing techniques. The parameters for conventional powder-metallurgical and Powder injection moulding production of iron for biodegradable medical implants were determined. With the application of these parameters an part with sufficient granulometry and green density, porosity after sintering, hardness, microhardness, tensile test and metallography. The comparison of samples with different sintering temperatures revealed that a slight variation of the sintering temperature can have a considerable effect on the physical and mechanical properties of iron for biodegradable medical implants. Keywords: Biodegradable metal Conference: 10th World Biomaterials Congress, Montréal, Canada, 17 May - 22 May, 2016. Presentation Type: Poster Topic: Biomaterials in microdevices and microarrays Citation: Martins V, Tavares AC, Schaeffer L and Wermuth D (2016). Powder metallurgical processing of iron for biodegradable medical implants: Physical and mechanical. Front. Bioeng. Biotechnol. Conference Abstract: 10th World Biomaterials Congress. doi: 10.3389/conf.FBIOE.2016.01.03041 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 27 Mar 2016; Published Online: 30 Mar 2016. Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Vinicius Martins André C Tavares Lirio Schaeffer Diego Wermuth Google Vinicius Martins André C Tavares Lirio Schaeffer Diego Wermuth Google Scholar Vinicius Martins André C Tavares Lirio Schaeffer Diego Wermuth PubMed Vinicius Martins André C Tavares Lirio Schaeffer Diego Wermuth Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Influence of binder system and temperature on rheological properties of water atomized 316L powder injection moulding feedstocks

Hatasiz toz enjeksiyon kaliplama (TEK) islemi icin besleme stoklarinin reolojik ozellikleri iyi bilinmelidir. Bu calismada 316L paslanmaz celik tozunun reolojik ozelliklerine baglayici sisteminin etkisini belirlemek amaciyla 2 farkli baglayici sistemi kullanilarak besleme stoklari hazirlanmistir. Deneysel calismalarda 20 mikron alti su atomize 316L paslanmaz celik tozu kullanilmistir. Heptan icerisinde cozunebilen parafin wax (PW) esasli ve su icerisinde cozunebilen polietilenglikol (PEG) esasli iki farkli baglayici sistemi hazirlanmistir. Her iki baglayici sistemi icerisinde iskelet baglayici olarak polipropilen (PP) ve yaglayici olarak stearik asit (SA) kullanilmistir. Baglayici sistemleri kuru olarak turbula marka 3 boyutlu karistiricida 30 dakika karistirilarak hazirlanmistir. Toz ve baglayici sistemleri kullanilarak hazirlanan besleme stoklarinin reolojik ozellikleri kilcal reometre kullanilarak karakterize edilmistir. Kilcal reometrenin sicakligi 150-200 °C araliginda basinc degerleri ise 0.165-2.069 MPa arasinda degistirilmistir. PEG esasli baglayici sistemi kullanilarak hazirlanan besleme stoklarinda toz tasima kapasitesi hacimce %55’e, PW esasli baglayici sistemi kullanilarak hazirlanan besleme stoklarinda ise %61’e cikartilmistir. PEG esasli besleme stoklarinda en dusuk viskozite degeri 304.707 Pa.s olarak, PW esasli besleme stoklarinda en dusuk viskozite degeri 48.857 Pa.s olarak elde edilmistir.

Prediction of density variation in powder injection moulding-filling process by using granular modelling with interstitial power-law fluid

In the present study, granular modelling with an interstitial power-law fluid was used to simulate the filling process in powder injection moulding (PIM). The granular model enables direct prediction of the density distribution. The feedstock, consisting of stainless steel powder and a multicomponent binder system, was injected in two moulds with designed features to verify the simulation results. The effects of the moulding parameters on the homogeneity of the powder particle distribution were investigated. The experimental results agreed well with the predictions. The results indicated that the granular model presented herein could be used for mould design and the determination of injection parameters.

Powder injection molding of Stellite 6 powder: Sintering, microstructural and mechanical properties

The purpose of this study was to produce Co-based Stellite 6 superalloy components by using the method of Powder Injection Molding (PIM) and to characterize the microstructural and mechanical properties of the produced components. The experimental studies were started through the formation of feedstock by mixing Stellite 6 powder with a multicomponent binder system. Prepared feedstock was formed by utilizing powder injection molding technique. Then the molded samples were subjected to the solvent and thermal debinding processes. Different sintering cycles were applied to the raw components for the purpose of determining the optimum sintering conditions. The densities of the sintered components were determined in accordance with the Archimedes' principle. The microstructural characterization was performed through scanning electron microscope (SEM) analysis, energy dispersive spectrometry (EDS) analyses, and X-ray diffraction (XRD) analysis. Hardness measurement and tensile test were conducted in order to determine the mechanical properties. The results illustrated that the injection molded Stellite 6 components were composed of fine and equiaxed grains, plenty of carbide precipitates exhibiting homogenous distribution throughout the microstructure formed at the grain boundaries and thus the mechanical properties were considerably high.

Powder injection moulding of multi-material devices

An important goal in research and development (R+D) is to enhance powder injection moulding (PIM) to combine two or more materials with different properties in a single piece manufactured in one process cycle. A further advantage is the considerable reduction of mounting costs.In principle, a certain range of options should be suitable for creating multi-component products. An important option is two-component PIM which is mainly characterized by a sophisticated sintering procedure taking into account the kinetics of all powder types involved. Investigations into how to fabricate immobile or mobile ceramic shaft-wheel components have been carried out successfully and even metal and ceramic materials can be connected for fixed joints.A further opportunity is opened up by In-mould Labelling PIM which uses powder filled tapes as the first component. Here again particular attention has to be paid to the sintering procedure, but if this is done, samples containing nano-sized powders in the surface area of the whole body can be obtained.

Effects of Micro and Nano Sized SiC Powder on the Rheological Properties of Al Based Feedstocks for Low Pressure Injection Molding

This study investigates the effects of micro- and nano-sized SiC powder on the rheological behavior of Al based feedstocks for powder injection molding (PIM). Different compositions of Al feedstocks with additions of micro and nano-SiC powder were prepared and their rheological properties were measured with a rotational rheometer. The effects of SiC content and shear rate were investigated and activation energies were compared amongst the feedstocks. The results showed that nano-SiC powder has a prominent effect on the viscosity and yield stress whereas micro-SiC does not have an effective role and the base micro-Al powder determines the overall rheological behavior of the feedstock. It was found that the feedstocks reveal pseudoplastic behavior at low shear rates and dilatancy at high shear rates. The critical shear rate (γcrit) was 100 s-1 for changing the rheological behavior. The activation energy of a given feedstock was found to increase with micro-SiC content while the reverse trend was observed for nano-SiC.

Material characterisation to identify the rheological behaviour for powder injection moulding

Abstract For the purpose of powder injection moulding, a specific method is presented to identify the parameters for a combined rheological constitutive model. This model is a combination of three models used in powder injection moulding and accounts for the effects of the temperature, shear rate and particle size of the powder. The data obtained from experimental measurements were used for identification of the model parameters. The model with identified parameters could be used to realize accurate simulations.

Simulations and injection molding experiments for aluminum nitride feedstock

Powder injection molding (PIM) simulations are useful for predicting mold-filling behavior because they aid in material, process and part design. To perform PIM simulations, measurements for feedstock properties such as physical, thermal, and rheological are required as input parameters. The availability of data for such feedstock properties is limited and fresh measurements are often required in order to perform PIM simulations for variations in feedstock composition. A recent study by our group presented a procedure to estimate feedstock properties and use them in mold-filling simulations. The present work compares the predictions of PIM mold-filling simulations using experimental and estimated feedstock properties with injection-molding experiments. Aluminum nitride (AlN) feedstock of 80.5wt% was compounded using a twin-screw extruder and injection-molded as tensile bars. Injection-molding experiments were performed using the AlN feedstock at various melt temperatures and injection pressures to obtain complete and partially filled parts. Simulations were performed using measured and estimated AlN feedstock properties on the tensile-bar geometry used during injection molding experiments. Melt temperature was varied while performing simulations to obtain a process window for complete and partially filled parts. A comparison between injection molding experiments and simulations was made to understand the dependence of the estimated and experimental feedstock properties in predicting mold filling behavior.

Thermoplastic filled with magnetocaloric powder

Abstract Magnetic refrigeration is an innovative and promising alternative to traditional refrigeration systems. This technology does not require refrigeration gases and offers a high thermodynamic efficiency, reducing the global environmental impact associated with the process. However, the production of magnetocaloric components used as regenerators in magnetic refrigeration systems is a significant challenge. This work consists of developing an innovative process to obtain magnetocaloric components by powder injection or extrusion moulding. A component containing up to 91.5 wt.% magnetocaloric powder was obtained using a gas atomised magnetocaloric powder La–Fe–Si alloy patented by Erasteel. The powder is first mixed with a thermoplastic polymer to obtain a “ready to shape” feedstock. Then, the feedstock is either injected or extruded to obtain the magnetocaloric component. Characterisations of the thermo-physical and mechanical properties are carried out during all stages of processing, from pure powder to injected parts. A study on the modification of the Curie temperature as a result of dehydrogenation was performed during each processing stages. Good processability was demonstrated for the highly loaded feedstock and conservation of the magnetocaloric properties during the process. Finally, the process does not induce any mass loss and allows the production of stable pieces containing a giant magnetocaloric effect.

The effect of aging treatment on the fracture toughness and impact strength of injection molded Ni-625 superalloy parts

In this study, the effect of aging heat treatment on fracture toughness and impact strength of Ni-625 superalloy fabricated by using powder injection molding (PIM) method was examined. After a feedstock was prepared by mixing the prealloyed Ni-625 superalloy powder, which was fabricated by gas atomisation, with a polymeric binder system and then it was granulated, it was shaped through the use of injection. The molded specimens were sintered at 1300°C for 3h after a two-stage debinding process. Once the sintered specimens were treated in the solution at 1150°C for 2h, they were quenched. Aging treatment was performed by keeping specimens at 745°C for 22h. Fracture toughness and impact tests were performed on sintered and aged specimens. Microstructure examinations were performed by using optical microscope, scanning electron microscope, and transmission electron microscope. The results revealed that aging heat treatment led to the formation of some carbides and intermetallic phases in the microstructure. While the hardness of the aged specimens increased due to these phases, their fracture toughness and impact strength values decreased.

Effects of binder system and processing parameters on formability of porous Ti/HA composite through powder injection molding

Abstract Porous titanium-hydroxyapatite (Ti/HA) composite is a developed composite material suitable for bio-medical applications. Powder injection molding (PIM) with space holder method is used to produce porous Ti/HA with mechanical properties, similar to human bone, and pores helps to initiate tissue growth. However, the differences in physical and mechanical properties of these composites are the main challenges during debinding and sintering. Therefore, the main objective is to determine effects of binder systems and processing parameters on formability of Ti/HA composite. In PIM, a binder system is necessary to produce green and ultimately sintered part. There are two binder systems and variation of sintering temperature has been used. Results revealed that Polyethylene glycol (PEG)-based binder system is applicable with NaCl space holder and optimum sintering parameters, including temperature, heating rate, and holding time of 1300 °C, 10 °C/min, and 5 h, respectively. The fabricated porous Ti/HA exhibits average porosity, pore size distribution, compressive strength, and roughness values of 55%, 60 μm to 170 μm, 370 MPa, and 0.323 μm, respectively. FESEM results showed that the pores are interconnected. It may be an appropriate material for future bio-medical applications.

The development of powder injection moulding binders: A quantification of individual components' interactions

The study of interactions between binder system components is critical for improving the processing properties of powder injection moulding (PIM) feedstocks. In this paper the interactions between acrawax (AW) and polyethylene glycol (PEG) were analysed and compared with those obtained for carnauba wax (CW). Due to the complexity of interaction mechanisms, the polymers were substituted with their basic low molecular weight analogues and analysed by FTIR and calorimetry. Self-interaction energies and association energies were determined using calorimetric analysis. Shifts of FTIR absorption peaks (C–O stretch and N–H stretch) served as evidence of the presence of interactions between the components. The calorimetric study of AW/PEG analogues showed a temperature increase during mixing, indicating the presence of strong interactions. The combined data from FTIR and calorimetry allowed a quantitative evaluation, which indicated about two times stronger interactions between AW (with CO and N–H groups) and PEG (with C–O and –OH groups), as compared to CW (with CO and C–O groups) and PEG analogues.

Application of Statistical Analysis in the Powder Injection Molding (PIM) of Mullite

In this work, the statistical analysis methods, including least square method and statistical hypothesis testing, were used to study the flexural strength and density of the specimens formed from mullite powder by powder injection molding (PIM). The feedstock for PIM consist of mullite powder and the composite binder consisting of 78 wt% polyethylene glycol (PEG), 20 wt% polyvinyl butyral (PVB), and 2 wt% stearic acid (SA). The PIM machine used in this work was the lab-scale plunger type. The compositions of the feedstock that could be injection molded by this machine were 50, 52, and 54vol% mullite. After molding, PEG in the green specimens was removed prior to sintering by soaking the specimens in the water at 60 °C for 24 hours while PVB and SA were removed during sintering. The sintering temperatures were 1300 to 1450°C. At significance level of 0.05, the least square method and the statistical hypothesis test showed that both feedstock compositions and sintering temperatures used in this work affected the densities of sintered specimens. However, the increasing of the flexural strength of sintered specimens was mainly by the increasing of the sintering temperature.

Effects of Water Temperatures on Water-Soluble Binder Removal in Ceramic Materials Fabricated by Powder Injection Moulding

This work focuses on the debinding conditions of the ceramic materials fabricated by powder injection moulding. Ceramic powder materials, including alumina and alumina-based composites were prepared as feedstocks and mixed with water-soluble polyethylene glycol (PEG) and polyvinyl butyral (PVB). The PEG/PVB binder mixture, with PEG to PVB ratio of 85:15 by weight and powder loading of 44 vol%, were thoroughly mixed and injected into the mould at the temperature of 190 °C to obtain rod-like specimens. Prior to sintering, the as-injected specimen was then leached in water, the temperature of which was varying from 30 (ambient temperature), 45 to 60 °C, in order to get rid of PEG and leave the specimens in shape by PVB. The rate of PEG removal according to different water temperatures was investigated. The experimental results suggested that PEG could completely be eliminated by 45 and 60 °C water without any dimensional disintegration in 5 hours whereas those leached in 30 °C water showed only 70% PEG removal. Higher water temperatures led to fast PEG removal rate at the beginning and then gradually decreased with elapsed times.

Microstructure and Properties of Zirconia Toughened Alumina Fabricated by Powder Injection Moulding

Zirconia toughened alumina (ZTA) ceramic has been fabricated by the powder injection moulding process. The ZTA ceramic, composed of 80 wt% alumina and 20 wt% zirconia, was mixed with a water-soluble, multi-component binder system. The binder ingredients were polyethylene glycol (PEG), polyvinyl butyral (PVB) and stearic acid (SA). Powder injection moulding was performed with powder loadings in the range of 48-52 vol%, using a laboratory-scale injection moulding machine. Water leaching was used for partial binder removal prior to thermal debinding and then sintering at 1650 °C for 2 hours. Microstructural examination of the ZTA ceramic revealed that zirconia inhibited alumina grain growth and, therefore, improved the mechanical and physical properties of the specimens. It was found that powder loading had an influence on density, hardness and strength of the specimens. A flexural strength of 334 MPa and hardness value of 2093 kg/mm2 was obtained from specimens injection moulded with 52 vol% powder loading feedstock. The highest sintered density achieved was 97% of the theoretical value.

Nano-hydroxyapatite-coated metal-ceramic composite of iron-tricalcium phosphate: Improving the surface wettability, adhesion and proliferation of mesenchymal stem cells in vitro

Thin radio-frequency magnetron sputter deposited nano-hydroxyapatite (HA) films were prepared on the surface of a Fe-tricalcium phosphate (Fe-TCP) bioceramic composite, which was obtained using a conventional powder injection moulding technique. The obtained nano-hydroxyapatite coated Fe-TCP biocomposites (nano-HA-Fe-TCP) were studied with respect to their chemical and phase composition, surface morphology, water contact angle, surface free energy and hysteresis. The deposition process resulted in a homogeneous, single-phase HA coating. The ability of the surface to support adhesion and the proliferation of human mesenchymal stem cells (hMSCs) was studied using biological short-term tests in vitro. The surface of the uncoated Fe-TCP bioceramic composite showed an initial cell attachment after 24h of seeding, but adhesion, proliferation and growth did not persist during 14 days of culture. However, the HA-Fe-TCP surfaces allowed cell adhesion, and proliferation during 14 days. The deposition of the nano-HA films on the Fe-TCP surface resulted in higher surface energy, improved hydrophilicity and biocompatibility compared with the surface of the uncoated Fe-TCP. Furthermore, it is suggested that an increase in the polar component of the surface energy was responsible for the enhanced cell adhesion and proliferation in the case of the nano-HA-Fe-TCP biocomposites.

Development and Characterization of Polymer Mixture (Binder) Based on Polyethylene Glycol (PEG) for a Superalloy A-286 to Powder Injection Moulding (MIM) Process

Metal injection moulding (MIM) has over the past decade established itself as a competitive manufacturing process to produce in large quantities small precision components with complex shape which would be costly to produce by alternative methods. In this process, during the injection phase, segregation appears in the feedstock and defects will be appears in the component during the sintering. To limit this effect, during decades a vast variety of binder systems have been developed. Binder systems are formulated as a mixture of different organic or inorganic substances with several functions. Binder system has the main commitments of giving the necessary rheological behavior to the feedstocks for injection moulding to transport the powder particles into the mould cavity and the cohesion of the green part.In this paper a study of the behavior of binders based on polyethylene glycol (PEG) and feedstocks based on superalloy A-286 powder were investigated by Fourier Transform InfraRed spectroscopy (FTIR) coupling with rheology. This methodology permits to compare the rheological behavior of the materials with the thermal behavior of the binder at a temperature close to the temperature of injection. Analyzes was made for the mixing and injection process. It is shows relationship between interactions and miscibility of polymer and influences on the rheological and mechanical behavior. All methodologies revealed no chemical interactions between the powder and the binder. This result shows the formulation of binder for the superalloy A-286 is not homogenous and the PEG is degraded under mixing and injection process conditions of this kind of formulation of feedstock.