MIM technology to feature prominently at Euro PM2007 Toulouse, 15-17 October 2007

Metal injection moulding (MIM) related presentations are set to be a highlight of the European Powder Metallurgy Association’s annual conference in Toulouse, France, 15-17 October 2007. The following sessions focus on MIM technology and include a special workshop on ‘Designing for MIM’. For registration information visit www.epma.com

Session 10: Powder Injection Moulding 1

Development of a Composite Porous/Dense Titanium Dental Implant Using a MIM Preform
Baril, E IMI-NRC, Boucherville, Canada

Dental implants are posts that are placed into the jawbone to take the place of missing tooth roots. They provide means of replacing lost teeth and restoring natural dental function. New implant designs with porous coating have been proposed to enhance osseo-integration and the bone-implant interface. This paper presents the development of a composite porous/dense dental implant based on two powder metallurgy approaches: Metal injection moulding (MIM) of titanium for the dense core and titanium foam coating for the outer surface. The focus of this paper is toward the production of the dense core using MIM technology. The mould design was done with the aid of full 3D injection moulding simulation. The MIM feedstock was made of plasma atomized CpTi-Grade 1 powder and a wax based binder. The variability of the process on some specific features is described and the microstructure of the final implant (with titanium foam coating) is presented.

Net-Shape Processing of NiTi Alloys by Micro Metal Injection Moulding (Micro-MIM)
Imgrund, P Fraunhofer IFAM, Bremen, Germany

Nickel-Titanium alloys have been of high research interest in recent years due to their shape memory and superelastic properties, making them especially suitable as actor devices. Micro Metal Injection Moulding (µ-MIM) can open up new fields for applications for small NiTi parts of complex geometry, for example in biomedical or transport applications. For setting up the µ-MIM process for this material, investigations were conducted using very fine prealloyed NiTi powders. Micro tensile test specimens were moulded and subsequently sintered under Argon atmosphere using different heating rates and dwell temperatures. Density up to 97 % was obtained after sintering. Oxygen and carbon contents were found to decrease with increasing heating rate. High amounts of NiTi phase were found by means of EDX analysis. Additionally some Ti2Ni and Ti-rich secondary phases were detected. DSC measurements were carried out after different heat treatments to determine phase transformation temperatures.

Highly Porous NiTi Components Produced by Metal Injection Molding in Combination with the Space Holder Method
Kühl, M Forschungszentrum Jülich GmbH, Jülich, Germany

Porous NiTi is a promising material for bone implants due to its bone-like mechanical and pseudoelastic behaviour. The combination of the space holder method (SHM) with the metal injection moulding (MIM) process has a high potential for the near-net-shape production of porous NiTi components. The MIM process with pre-alloyed NiTi powder avoids the expensive and difficult thermomechanical working, the machining and high losses of the starting material. The SHM guarantees a well defined pore size distribution with total porosities up to 70%. In the present study, NaCl, saccharose and PMMA were investigated regarding their suitability as space holder materials. Different pore sizes and shapes in the range of 100-500 µm were achieved using these space holders. The shape memory effect is demonstrated by differential scanning calorimetry (DSC) and by mechanical compression tests. Defiances and the general applicability of the MIM process in combination with the SHM are discussed.

Micro Metal Powder Injection Moulding By LIGA Lost Form Technology and Using Nano-size Metal Particle
Nishiyabu, K Osaka Prefectural College of Technology, Osaka, Japan

The micro metal powder injection moulding using sacrificial plastic mould (SP-mould), namely micro SP-mould insert MIM process has been developed to solve the problems specific to µ-MIM, e.g. difficulty of filling feedstock in narrow cavities and de-moulding minute green compacts from the cavity. This study aims to improve the quality of micro-structured parts manufactured by LIGA/µ-SPiMIM process and to know the problems to be solved by using nano-sized metal particle. A PMMA resist film, which was prepared by irradiation process in LIGA, was used as SP-mould. The novel injection moulding machine which can achieve to mould without pelletizing was used to produce the tiny specimens with high trial efficiency and a small amount of feedstock. The effects of particle size on the quality of sintered parts were investigated. It was concluded that finer powder was better for transcription than coarser ones, but nano-sized metal powder also has accompanying technical issues which need to be modified to ensure good quality of sintered parts.

Session 14: Powder Injection Moulding 2

New Method to Detect Flaws of High- and Medium-Pressure PIM Feedstocks
Gornik, C Battenfeld Kunstoffmaschinen GmbH, Kottingbrunn, Austria

The flowability of feedstocks is usually used to characterize their consistency. Mistakes in the binder/powder ratio and in the mixing homogeneity can be detected by viscosity measurements. Various methods for testing the viscosity are known and described in the literature, e.g. melt-indexer, capillary viscosimeter, RheoNoz (rheological nozzle) etc. Each method has its specific advantages but also its specific disadvantages. Typical factors taken into consideration for choosing a proper method for feedstock characterization are the costs and the time needed for measuring. The paper presents a new apparatus for a quick check of the feedstock consistency which is based on a by-pass nozzle of the injection moulding machine. During PIM-parts production and between two consecutive shots the injection moulding machine injects the molten feedstock through a capillary die. The pressure needed to keep a certain speed is used as an indicator for the flowability and therefore the quality of the feedstock. The applicability of the method with a polystyrene and a high-pressure PIM feedstock will be presented.

Experimental and Numerical Analysis on the Densification Behaviours of the Metal Injection Moulded Components
Barrière, T ENSMM, Besancon, France

In the sintering stage of Metal Injection Moulding (MIM), the components undergo the large shrinkages. A phenomenological model for sintering based on continuum mechanics is employed to predict the dimensional changes of sintered parts. The bending tests during sintering and the dilatometeric tests are used to determine the uniaxial viscosity and sintering stress in the sintering model. The factors that can induce uneven shrinkages, such as the green inhomogeneity, gravity and friction, are considered in the finite element simulations. A demonstration of the sintering simulation for a part in wheel shape is presented and compared with the experimental results.

Injection Moulding and Tool Design Development at Sandvik Tooling
Micski, A Sandvik Tooling, Stockholm, Sweden

Sandvik Tooling utilises injection moulding as a forming process for cemented carbide products with complex shapes. However, the design and manufacture of new moulding tools are costly and time consuming. In order to render the mould development more efficient, simulations of the injection moulding process are used. Design issues such as gating positions, filling profiles, or possible gas inclusions can be evaluated using a simulation tool. An important input to the simulations is the rheological properties of the feedstock and its dependence on temperature and composition. In this paper, some examples on how Sandvik utilises simulations and rheological evaluations as working methods for tool design and characterisation of the feedstock will be presented.

Disposable Insert Material Selection for Internal Undercut Features in Powder Injection Molding
Josef, V Advanced Materials Technologies Pte Ltd, Singapore

Undercut features have always been a problem with injection molding. The features require complicated mold design with corresponding higher mold fabrication cost. In certain cases, undercut features are entirely impossible to achieve by injection molding. Using a disposable insert material, which is molded together with the part and is later removed, is a cost-effective solution to undercut features. In powder injection molding, the most suitable candidate for insert material are degradable polymers, being easily molded and burned-off during sintering.

The process of selecting insert material has several considerations, among others are: moldability, ability to withstand the molding temperature, easy removal without imparting stress on structural integrity of the part, and ability to produce relatively smooth inner surface. The objective of the paper is to illustrate the material characteristic considerations when choosing disposable insert material in powder injection molding involving complex internal undercut features.

Session 18: Powder Injection Moulding 3

Influence of Gas Atomised Powder Size on Mechanical Properties of 15-5PH
Kearns, M Sandvik Osprey Ltd, Neath, UK

Control of mechanical properties and surface roughness in MIM products is critical to their competitiveness against other fabrication methods. Material cost is also often cited as a barrier to further penetration of MIM technology. In this study we investigate the impact of starting particle size distribution on the sintering performance and finished properties of a precipitation-hardened stainless steel. The performance of conventional 90% -22µm powder is compared with -32µm and -38µm powders which are prepared by sieving as opposed to classifying with consequent cost benefits. Rather than the more popular 17-4PH system, the 15-5PH alloy is investigated with a view to control of Cu loss during furnacing and also moderation of final hardness after furnace cooling. Results from 3-point bend and tensile testing are presented alongside microstructural analysis. Commercial aspects of the use of coarser powders are discussed.

Improvement of Rheological Properties of a MIM Superalloy (Inconel 718) Feedstock using Different Powder Particle Sizes
Contreras Andujar, J M Universidad Carlos III de Madrid, Madrid, Spain

One of the most important stages in the MIM process is the feedstock fabrication and its injection moulding, where the rheological properties are of crucial importance. In this work, the possibility of changing the powder usually used in MIM (particle size ?20 µm) by powder mixtures made with different particle size ranges was carried out to study the flow behaviour of the feedstocks. In this way, five Inconel 718 feedstocks were prepared with the same binder (HDPE-paraffin wax-stearic acid), mixing four different sizes of spherical gas atomised powder (lt;22 µm; 16-45 µm; 45-63 µm; 65-212 µm). The rheological properties from the feedstocks were evaluated with a capillary rheometer to study the characteristics and processability of each one by measuring different rheological parameters such as flow index, yield stress and activation energy.

Rheological Properties of M2 HSS Feedstock Designed for Metal Injection Moulding
Herranz, G Universidad de Castilla La Mancha, Ciudad Real, Spain

This work is focused in the evaluation of the rheological properties of a wax-HDPE binder formulations and M2 High Speed Steel feedstock designed for metal injection moulding (MIM). The rheological properties were characterized by a capillary rheometer. Through these measurements the critical powder loading (CPVC) of the feedstock was determined to obtain a suitable feedstock for MIM with optimal powder content (68 % vol.). The viscosities of the formulations have been evaluated on the basis of the shear rates and shear stresses values measured. From the capillary rheometer curves the flow behaviour index (n) was determined to be less than 0.5 which indicates a pseudoplastic behaviour. Effect of the temperature onto the viscosity was also studied based on the determination of flow activation energies of each formulation. The rheological characterization allows us to produce an optimal feedstock for MIM that it was successfully injected obtaining high quality green parts.

Manufacturing of Ceramic-Metal Composites Using Multi-Component Injection Moulding
Baumann, A Fraunhofer IKTS, Dresden, Germany

The implementation of multi-component injection moulding (well known in polymer shaping) into powder technology offers the possibility to create composite materials made of ceramics and metals. In the co-shaping process the different materials, e.g. ZrO2 and steel 17-4PH, are directly injected into one mould. In the subsequent step of co-firing the part is debindered and sintered up to nearly theoretical density. Up to now, the advanced research on multi-component powder injection moulding has led to a variety of different methods: sandwich injection moulding allows the manufacturing of parts considering a core-cover aspect, assembly moulding offers the possibility to produce devices whose components are free to move against each other, and inmould labelling leads to material compounds with unexpected high aspect ratios. Access to this revolutionary manufacturing technology can be obtained by realizing those strategies that lead to a stable material compound between ceramic and metal during co-sintering. The adjustment of the absolute sintering shrinkage in the combined powder packages can be seen as fundamental requirement for successful co-sintering.

Session 23: Powder Injection Moulding 4

2C-molding for MIM
Hartwig, T Fraunhofer-IFAM, Bremen, Germany

Two colour Metal Injection Moulding has received some interest. It is expected that it will allow even more functionality in one MIM part by combining two materials or reduce cost by coating an inner section made of cheaper powder with a layer of the more expensive powder. These two cases need an intact and sound interface between the materials other than the assembly moulding which has been proposed last year. In this paper the focus is set on the moulding stage of the 2C-MIM, discussing the various parameters influencing a good connection between materials injected into a tensile test sample. This is done using Catamold feedstocks as a standard on a 2C molding machine.

Optimisation of the Sintering Atmosphere for Metal Injection Moulding of Gamma TiAl Alloy Powder
Ebel, T GKSS Research Centre Geestacht GmbH, Geesthacht, Germany

Test specimens made from fine Ti 47Al 4(Mn,Cr,Nb,Si,B) (at%) powder were produced by metal injection moulding (MIM). In order to overcome the problem of the Al-loss the effect of different sintering atmospheres on the homogeneity of the specimen’s microstructure was investigated. The combination of changing pressure from 600 mbar argon to high vacuum with the provision of an Al-rich atmosphere by a donator material and a succeeding heat treatment led to a microstructure of the sintered part consisting solely of near-gamma phase.

Qualification of Material DIN 1.4404 (316 L) for Liquid Hydrogen Storage Applications
Zauner, R Austrian Research Centres GmbH, Seibersdorf, Austria

316 L (DIN1.4404) is known to be the most commonly used material in metal injection moulding. In search for new applications of MIM, the material DIN 1.4404 has been tested for its mechanical properties under liquid hydrogen conditions (-253oC). Tensile bars and impact strength test bars were injection moulded and sintered to different porosities and the material testing performed under room temperature, liquid nitrogen (-196oC) and liquid helium (-269oC) temperatures. For the fully dense samples it was shown that at room temperature an Rm of around 550 MPa and a ductility of 55%, at liquid nitrogen temperature an Rm of around 1350 MPa and a ductility of 38% and at liquid helium temperature an Rm of around 1500 MPa and a ductility of 22% could be achieved, showing impressively the increase in strength at cost of ductility at low temperatures. Additional characterisation data – including non destructive testing (NDT) data – of impact experiments at room temperature and liquid nitrogen temperature will be presented.

Microstructure and Mechanical Properties of a C Alloyed Co-Cr-Mo Produced by MIM
Muterlle, P University of Trento, Trento, Italy

The microstructure of as sintered C alloyed Co-29Cr-6Mo comprises a f.c.c. solid solution and carbides located at the boundary between the original powder particles. Carbides improve wear resistance of the Co alloy but, meanwhile, they can cause abrasion of the counterface material. This effect is critical in biomedical applications. Moreover, carbides decrease ductility and increase tensile strength. To modify the microstructure, a solubilisation heat treatment is carried out. It dissolves carbides and partially transforms the hcp matrix in a fcc. solid solution. The tensile properties are then modified, increasing ductility and decreasing strength.

Sintering was carried out in vacuum, and a special treatment was experimented, to combine sintering and solubilisation in one step.

SPECIAL WORKSHOP: DESIGNING FOR MIM

Design for PM: A Project Funded by the Leonardo Programme
Wroe, J, EPMA,

Design for PM is a two-year EU funded project with twelve partners comprising industry, academia and training providers, coordinated by the EPMA. The outcome of the project will be a modular e-learning course targeted mainly at industrial designers and engineers. It is intended that their increased understanding of the design parameters specific to PM will enable them, with help from their suppliers, to design superior components/products to be manufactured using the powder metallurgy process.

The main target sectors are the automotive, construction and light engineering industries. One specific target group will be in Central and Eastern Europe, which is an area with high growth in auto production/design and this will be addressed using our Slovakian partner. As a further target the content will be incorporated by universities into their courses for students in relevant subjects, with the objective of educating the designers and engineers of the future. The project will be completed in October 2008.

MIM Success in the Automotive Industry: Material and Design
Langer, I Schunk Sintermetalltechnik GmbH,

Multifunctional complex parts produced by MIM are commonly used in the automotive industry. Mostly, MIM produced parts are permanently in competition with investment casted or punched parts. To be successful in this situation it is necessary to implement the advantages of the MIM technique into a project as early as possible. Such advantages can also be seen in material composition as well as in design possibilities. Based on several selected serial MIM parts for automotive applications, the advantages of the MIM technique, will be discussed, as well as the reasons of success compared with conventional manufacturing techniques. Different methods of material composition (mixture of element powders, masteralloys, ready alloyed powders and/or a combination of these) and their influence on material properties will be compared. Finally, complex design solutions developed to substitute up to 8 conventional manufactured parts will be presented.

Inverse Approach to Selection of Component Designs for Metal Powder Injection Molding
German, R MSU-CAVS, USA

The production of components by the metal powder injection molding (PIM or MIM) process is analyzed from an inverse view. To accomplish this goal, several hundred production parts are analyzed for features (length, mass, slenderness, wall thickness ratio, complexity, cost, and such). An inverse approach assumes those that have passed into production satisfy the major technical and economic criteria. Accordingly, the database provides a definition of the design window for this technology. Such a reverse approach provides the first design guidelines rationalized to what actually reaches production status. Components with the proper blend of attributes have a high probability for success against competitive technologies. The most suitable components tend to be less than 25 mm in size and less than 10 g in mass, are slender, and have high complexity.

Development of a MIM Jig Saw Blade Holder Assembly
Breitenmoser, G Parmaco Metal Injection Molding AG,

After having manufactured a MIM jig saw holder for several years it was desired to have a new design which would allow for fast blade replacement. Already the old MIM jig saw holder had replaced an investment cast component and had led to considerable cost savings and improved quality. The goal of the new design was to develop a jig saw blade holder assembly which would fulfil the desired functions and the requirements for the MIM process. The resulting assembly contains two MIM parts, a tube manufactured by rotary swaging and several springs. The design, the hardening process, the joining process with laser welding, the surface treatment, the assembly and the end control are discussed. The fastener and pusher rod assembly is a prime example for MIM’s capabilities to give shape to the designer’s imagination. Moreover the assembly shows that today intricate MIM parts of Carbon steel can withstand critical loads even when welded. For further information and Euro PM2007 registration visit www.epma.com

Sessions and presentations as of August 9 2007