Two-component metal injection moulding of Ti-6Al-4V and stainless steel Bi-material parts

Two-component metal injection moulding (2C-MIM) allows producing functionallygraded metal parts of complex shape by co-sintering. Until now several studies have demonstratedthat different material properties can be combined. Another promising material combination istitanium and iron-based materials. It can combine the biocompatibility and low density of titaniumwith a ductile and cost efficient stainless steel. However, co-sintering these materials revealschallenges due to a significant mismatch in sintering shrinkage and limitations in sinteringtemperature for both materials. The recent study showed that Ti-6Al-4V can be joined to thestainless steel 316L by 2C-MIM provided that certain constraints are taken into account. Thequality of the interface before and after co-sintering is a crucial factor for intact parts afterprocessing. By applying sinterdilatometry the mismatch in shrinkage was compensated by usingadjusted powder characteristics and tailored feedstock compositions. A co-sintering cycle wasdefined with regard to the sintering characteristics of both materials. The developed two-componentspecimens revealed significant interdiffusion of alloying elements at the Ti-6Al-4V / 316L interfaceand a tensile strength of about 200 MPa after co-sintering

Combining different or even contrasting material properties using two-component metal injection moulding

Two-component metal injection moulding (2C-MIM) allows manufacturing multi-material MIM components with tailored properties. It can generate completely new design opportunities with enhanced functionality options for MIM products. Additional assembling operations are not required. Process improvements and extended experience concerning the interactions of powders at sintered interfaces advanced the 2C-MIM technology to the threshold to be launched for industrial production. In this paper, recent investigations on the process development for bi-material parts with contrasting properties as ferritic/austenitic stainless steel (magnetic/non-magnetic), steel/titanium (toughness/biocompatibility) and steel/cobalt chromium (toughness/wear resistance) are shown. The results showed that bi-material combinations can be achieved if the utilized powders and feedstocks as well as the process parameters are adjusted. Requirements for powder selection and methods to balance the shrinkage mismatches during co-sintering were developed and evaluated concerning processability, microstructure and bonding strength at the interface

Standards for Metal Injection Moulding: Progress to-date and future challenges

Metal Injection Moulding can today be considered as a maturing manufacturing technology for small, complex shaped metal components. A broad spectrum of materials is available for MIM production and a number of steels, titanium and titanium alloys, nickel superalloys and an increasing number of special materials such as copper, cobalt-chromium or tungsten are qualified for MIM. The need for new materials is primarily driven by upcoming applications in the automotive, aerospace and medical sectors. In order to help designers, engineers, manufacturers and customers to choose one manufacturing process over another for these new applications, it is very helpful if a reliable basis for comparison is available. Standardisation is an essential process to provide such a database of typically attain able results. In an exclusive report for Powder Injection Moulding International, Fraunhofer IFAMs Marco Mulser and Prof Dr Frank Petzoldt review progress to-date, summarise existing standards for MIM technology and consider the challenges that lie ahead in order to support the growth of new markets and applications

Anforderungen an Pulver und Formgebung magnetokalorischer Werkstoffe

Neue Materialentwicklungen in Bereich der magnetokalorischen Werkstoffe eröffnen die Möglichkeit, mittels magnetischer Kühlung leistungsstarke und weltfreundliche Kühlsysteme aufzubauen. Auf dem magnetokalorischen Prinzip basierende Kühlsysteme könnten zukünftig eine Alternative zu den bekannten Kompressor- Kühlverfahren darstellen und in Kühlschränke, Klimaanlagen oder Wärmepumpen integriert werden. Eine aktuelle Herausforderung stellt dabei die Umsetzuing der entwickelten Materialsysteme in technische Bauteile dar. Serientaugliche Formgebungsprozesse sind erforderlich, um vom derzeitigen Stand des Prototypenbaus zur industriellen Serienproduktion von magnetokalorischen Kühlelementen zu gelangen. Mit den pulvermetallurgischen Formgebungsverfahren der binderunterstützenden Extrusion und dem Metallpulverspritzguss stehen zwei endformnahe Fertigungsverfahren für die serientaugliche Verarbeitung von metalkalorischen Materialien zur Verfügung. Notwendige Voraussetzung ist dafür die Bereitstellung einer entsprechenden Pulverqualität des magnetkalorischen Materials, welche insbesondere für die Herstellung von dünnwandigen und mikrostrukturierten Bauteilen von großer Relevanz ist. Die pulverbasierten Additiven Fertigungsverfahren, wie beispielsweise das Selektive Laserschmelzen, bieten das Potential, eine noch höhere Geometriefreiheit für magnetkalorische Wärmetauschstrukturen zu ermöglichen. Zusätzlich können aufgrund der besonderen Verarbeitungsbedingungen beim SLM spezielle Materialzustände eingestellt werden. Bestehende Herausforderungen für die Anwendung dieser Verfahren sind unter anderem der Oxidationsschutz der sauerstoffaffinen Materialien, die Optimierung der Verarbeitungsparameter für die jeweiligen Legierungen sowie die Auswahl geeigneter Ausgangspulver. Die stetige Weiterentwicklung der nötigen pulvermetallurischen Formgebungsprozesse zur Herstellung von Wärmetauschelementen tragen langfristig dazu bei, den Technologie- Reifegrad der magnetokalorischen Kühltechologie weiter voranzutreiben und eine mögliche Markteinführung magnetkalorischer Kühlsysteme zu beschleunigen. Für die pulververarbeitenden Industrien ergeben sich damit neue Chancen in einer noch jungen Materialklasse

Tungsten-copper / stainless steel Bi-material parts by 2C-MIM

The paper reports on investigations for two component injection moulding (2C-MIM) of bi-material parts of W-Cu and the stainless steel 316L. The feasibility of joining these different materials by co-sintering was investigated. A significant mismatch in shrinkage of tungsten and 316L was observed by sinter dilatometry. It could be compensated by adjusting the powder particle size of the stainless steel. MIM parts of both materials were sinter joined followed by infiltration with Cu powder. The tungsten-copper / stainless steel interfaces were characterized by optical microscopy. The results show that it is possible to produce an interface of tungsten-copper and stainless steel by co-sintering and infiltration. The material combination in a functionally graded part would combine the high electrical and thermal conductivity of W-Cu with a ductile and rather cheap stainless steel substrate predestinated for electrical and thermal management applications

Laser beam melting of technical springs: Additional functionality and powder quality control

Springs are applied in diverse shapes and sizes for a wide range of technical devices, machines and applications. Usually, they interact with many other components as part of an assembly to fulfil a joint function. Generally, springs are produced by coiling a drawn wire into multiple-turn windings around as haft or mandrel. Demands for miniaturisation and reduction of assembling operations require new spring designs that cannot be realised by coiling. The paper summarizes new design opportunities that Additive Manufacturing offers for complex-shaped springs. Additional functionalities for technical springs are highlighted. The focus is on the challenge of the addition and removal of support structures required for Laser Beam Melting (LBM) as well as powder quality control for the utilized material. New spring designs were achieved provided that specific design rules were followed

Influence of powder metallurgical processing routes on phase formations in a multicomponent NbSi-alloy

Refractory metal silicide composites on the basis of Nbss-Nb5Si3 have been investigated as potential alternatives for nickel-base superalloys for years because of their low densities and good high-temperature strengths. NbSi-based composites are typically produced by arc-melting or casting. Samples in this study, however, were produced by powder metallurgy because of the potential for near net-shape component fabrication with very homogeneous microstructures. Either gas atomized powder or high-energy mechanically alloyed elemental powders were compacted by powder injection molding or hot isostatic pressing. Heat treatments were applied for phase stability evaluation. Slight compositional changes (oxygen, nitrogen, or iron) introduced by the processing route, i.e., powder production and consolidation, can affect phase formations and phase transitions during the process. Special focus is put on the distinction between different silicides (Nb5Si3 and Nb3Si) and silicide modifications (α-, β-, and γ-Nb5Si3), respectively. These were evaluated by x-ray diffraction and energy-dispersive spectroscopy measurements with the additional inclusion of thermodynamic calculations using the calculated phase diagram method