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PM2010 World Congress: Session 16 - Powder Injection Moulding of Titanium
Tuesday morning, 12 October
Chairmen:
Professor Hideshi Miura, Kyushu University,
Dr Thierry Barrière ENSMM
Oral
Market and Technology for Titanium Metal Powder Injection Moulding
German, R (San Diego State University, San Diego, USA)
This analysis benchmarks both the current market information (powders, components, and applications) and underlying technology for metal powder injection molding of titanium and its key alloys. Attention is given to commercially pure grades of titanium (CP Ti), various common alloys (T-6Al-4V, Ti-6Al-7Nb) and compounds (TiAl, NiTi). The market development has been slow with more than 20 years of effort, ranging from running shoe spikes in 1991 to human implant applications. From a technology standpoint, we find that essentially everything is important. Highlights will be given on the most important processing steps to show how to optimize properties, including information on the powder, binder, feedstock formulation, mixing, molding, debinding, sintering, and post-sintering steps. Mechanical properties are linked to sintering time, sintering temperature, debinding cycle, and initial powder packing density and oxygen content. These results help optimize processing toward specific performance objectives. The barriers in Ti-PIM are noted along with research efforts.
Supercritical CO2 Debinding: Benefits to Titanium Powder Injection Moulding?
Thomas, Y (Industrial materials Institute - NRC, Boucherville, Canada)
Supercritical CO2 debinding has been described as a clean and environmentally friendly alternative to other debinding routes. The claims are that SC-CO2 should prevent oxidation, lead to less defects and reduce the debinding time. This appears therefore as the process of choice for titanium MIM since this material is very sensitive to contamination by interstitial elements during the whole process which, in turn, affects the mechanical properties and integrity required for demanding sectors such as biomedical. In this paper, the potential benefits of using the SC-CO2 technology for titanium MIM parts have been evaluated as a replacement for the conventional immersion in solvent process. The efficiency of the debinding processes (SC-CO2 and hexane) as well as their effect on final properties of titanium MIM dental implants, and in particular on interstitials composition (C wt.%, O wt.% and N wt.%) and dimensional variations will be presented and discussed, as a function of the processing debinding parameters.
Substantial Improvement Of Fatigue Behaviour Of Ti-6Al-4V Alloy Processed By MIM Using Boron Microalloying
Milagres Ferri, O (GKSS-Research Centre, Geesthacht, Germany)
Titanium boride particle (TiB) is considered to be an effective reinforcement for titanium since it can be synthesized in situ during process fabrication. Among the processes which are able to produce parts by using the in situ approach, powder metallurgy is the most prominent in terms of microstructure homogeneity. In this study, metal injection moulding (MIM) was applied in order to obtain Ti-6Al-4V components with and without boron addition. Samples with boron addition achieved higher densification than those without boron. Furthermore, electron back scattering diffraction (EBSD) technique was applied in order to elucidate and validate the observed microstructure morphology difference. Substantial increase of the yield stress from 720 MPa to 790 MPa and high cycle fatigue behaviour from 450 MPa to 640 MPa was obtained in the Ti-6Al-4V alloy processed by MIM and microalloyed by boron. It is proposed that the enhancement of the mechanical properties originates from the refined microstructure and particle reinforcement.
Poster
Effect of Neodymium on Oxygen Diffusion and Distribution of MIM Titanium
He, H (Central South University, Changsha, China)
This paper focused on the effect of neodymium (Nd) addition on oxygen diffusion and distribution of in titanium (Ti) prepared by metal injection molding (MIM). The reaction mechanism between oxygen and Nd, as well as the diffusion coefficients of oxygen in pure Ti and TiNd, has been investigated. It was demonstrated that the dissociation pressure of Nd2O3 is many orders of magnitude lower than that of TiO2. And therefore oxygen is more prone to react with Nd and it is possible to prevent Ti from been oxidized. The thickness of oxygen enriched layer in the TiNd specimens is thinner than that of pure Ti. The Nd particles in Ti matrix played an oxygen scavenger role and depleted oxygen around them. The diffusion coefficient of oxygen in pure titanium is an order of magnitude higher than that in TiNd and it can be inferred that Nd can effectively decrease the oxygen diffusion process in Ti.
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