Tuesday morning, 12 October

Chairmen
Professor Teresa Vieira, FCTUC
Dr Bruno Vicenzi, Mimitalia srl

Oral

Contribution To The Development Of 18 Carat Gold Alloy Shaped By MIM
Mulin, H (Ecole Catholique d'Arts et Métiers (ECAM), Lyon, France)

Metal Injection molding (MIM) is appropriate to small and complex-shaped components having good surface state. In comparison to parts manufactured by traditional process such as investment casting or forging, parts with better tolerances can be achieved. Hence MIM is a viable manufacturing method for the jewellery industry requiring also strong aesthetic criteria (brightness, colour, surface finish, smooth aspect …). Nevertheless due to the specific properties of precious alloy such as low temperature sintering for instance, MIM process application is not easily transposable from conventional used materials.

This contribution will focus on parts made of 18 carat gold alloy. This study supported by industrial partner highlights technical difficulties encountered at sintering step (heating rate, atmosphere effect…) and their consequences (non-sintered area, abnormal grain growth). Moreover post treatment effects (HIP) are investigated.

Effect Of Powder Loading On Rheology And Dimensional Variability Of Porous, Pseudo-Elastic Niti Alloy Produced By Metal Injection Moulding (MIM) Using A Partly Water Soluble Binder System
Ismail, M H (University of Sheffield, Sheffield, UK)

An alternative powder metallurgy route for producing porous NiTi alloy by metal injection moulding(MIM) of elemental Ni and Ti powders is being investigated. This alloy shows pseudo-elastic and shape memory behaviour. Using an atomic ratio of 50.9% Ni, three feedstock batches with different powder loadings ranging from 65.5vol% and 69.5vol% were prepared. The binder used was a partly water soluble system, comprising polyethylene-glycol(PEG), polymethyl-methacrylate(PMMA) and stearic acid(SA) with a mass ratio of 83/15/2. Rheological analysis was carried out at different temperatures and shear rates in order to investigate the homogeneity and flowability of the mixture. Cylindrical parts were moulded, water leached to remove the PEG, heated in Argon to remove the residual PMMA and sintered at 1250°C for 1 hour in vacum. The effects of powder loading on the as-sintered properties such as impurity content, dimensional variability, porosity, microstructure and compression behaviour are presented and discussed

Mechanical Properties of Powder Injection Moulded 17-4PH Sintered in Dissociated Ammonia
Hwang, K-S (National Taiwan University, Taipei, Taiwan)

The mechanical properties of powder injection moulded 17-4PH sintered in vacuum, hydrogen, and dissociated ammonia are compared in this study. When sintered at 1320ºC for 2 hours, the dissociated ammonia produced more austenite, which resulted in low sintered density and hardness, in contrast to the nitrogen strengthening effect on 316L stainless steels. However, this problem can be solved by using a higher sintering temperatures of 1350ºC and by adding ƒ¿-Phase stabilizers such as Mo. With higher sintering temperature and Mo addition, a hardness of 45 HRC and a density of 95% could still be attained when these sintered specimens were solution treated and aged. The changes in microstructure caused by the sintering atmosphere and Mo and the resulting effects on mechanical properties are discussed.

Influence Of Chromium And Vanadium Carbides Reinforcement On The Sintering Process Of M2 HSS Processing By MIM
Herranz, G (Universidad de Castilla la Mancha, Ciudad Real, Spain)

Metal matrix composites (MMCs) based on M2 HSS and reinforced with different percentage of chromium carbide (Cr2C3) and vanadium carbide (VC) manufactured by metal injection moulding route have been studied. The feedstock consists on metal powder reinforced with carbides and binder based on polyethylene and paraffin wax. The debinding process was carried out by thermal debinding and the cycle was designed using TGA studies of the feedstock. Then pieces were sintered in the atmosphere of the flowing N2-H2 gas in the range between 1200 and 1300ºC. To determine the optimal sintering temperature, the samples were characterized by microstructural analysis. The effects of sintering parameters on microhardness and density were studied. This research demonstrates that the powder injection moulding process is a suitable method for fabrication of the high-speed steel matrix composites. Grain growth and microstructure coarsening were retarded by the addition of the reinforcement.

Poster

The Influence of Powder Size on Processing and Properties of MIM 17-4PH
Murray, K (Sandvik Osprey Ltd, Neath, United Kingdom)

The benefits of Metal Injection Moulding (MIM) as a net shape manufacturing route for complex parts continue to be exploited in an ever increasing range of applications. It is Sandvik Osprey’s experience that the range of powder particle size distributions used in MIM has expanded in parallel with this market diversification. In this paper we investigate the influence of powder particle size distributions, from -32 µm to 90% -10 µm, on the sintering process and on the mechanical properties of 17-4PH stainless steel in the as sintered and heat treated condition. The effects of particle size on part distortion and surface finish are also examined. In addition, the effect of secondary consolidation by Hot Isostatic Pressing (HIPping) on mechanical properties of sintered 17-4PH MIM parts, is investigated.

Electroforming of Fe-Ni Alloyed Micro Mold for Powder Injection Molding
Son, S-H (Korea Institute of Industrial Technology, Incheon, S Korea)

In this study, the micro mold was made using electroforming process of Fe-Ni alloy for PIM of micro-gear.

Reaction mechanism of Fe-Ni alloy electrodeposition process making micro-gear mold was investigated using rotating disk electrode. To clarify the rate determining step, the activation energies of iron and nickel components were calculated from the Arrhenius plot in the temperature range of 308K and 348K. Experimental activation energies of iron and nickel were 9.14 kcal/mole and 5.61 kcal/mole, respectively. The electrodeposition rate of iron seems to be controlled partly by electrochemical reaction and partly by mass transport, namely mixed controlled. However, that of nickel seems to be controlled by mass transport predominantly. The mandrel which have 500 §­ in width and 600 §­ in depth for electroforming was prepared by UV-lithography processing using epoxy based photoresist. Subsequently, Ni-Fe micro-gear mold was fabricated with good hardness(690 Hv) and very low surface roughness(Ra 58μm).

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Related features for download:

• Characterisation of alumina feedstock with polyacetal and wax-polymer binder systems for micro powder injection moulding
• Metal injection moulding of a new Fe-8Ni micron-size pre-alloyed powder
• The processing of advanced magnetic components by PIM:current status and future opportunities
• Injection moulding opens up opportunities for high performance NdFeB magnets
• Influence of carbon content on microstructure and tensile properties of the 17-4 PH stainless steel produced by MIM