European Cells and Materials Vol. 26. Suppl. 4, 2013 (page 16) ISSN 1473-2262
http://www.ecmjournal.org
Porous titanium by powder injection moulding of titanium hydride and PMMA space holders
E. Carreño-Morelli
1, A. Amherd
1,2, M. Rodriguez-Arbaizar
1, D. Zufferey
1, A. Várez
2, J.-E. Bidaux
11
University of Applied Sciences Western Switzerland, 1950 Sion, Switzerland.
2University Carlos III of Madrid, 28911 Leganés, Spain
INTRODUCTION: Porous titanium is used as
implant material because of its high specific strength, bone-like stiffness, biocompatibility and good bone cell ingrowth provided that the open pores have sizes between 100 μm and 500μm. Powder metallurgy has been successfully used to produce titanium foams by using the space holder method [1-3]. Recently, Ti grade 4 has been obtained by powder injection moulding (PIM) of titanium hydride, which is cheaper and less reactive than pure titanium [4]. The feasibility of a novel route combining TiH2 and space holders to
produce porous titanium is explored in this work.
METHODS: The starting powder (Fig. 1) was
angular TiH2 (AG Materials Inc., Taiwan, median
particle size Dv50 = 20.26 µm). PMMA particles (polymethylmethacrylate) were used as space holders (Goodfellow, UK, Dv50 ~ 600 µm).
Fig. 1: TiH2 powder and PMMA space holders.
Feedstocks for PIM were prepared with a binder composed of low density polyethylene, paraffin wax and stearic acid. The solids loading was 60 vol.%, which includes equal parts of TiH2
(30 vol.%) and PMMA (30 vol.%). Compression test specimens (9 mm diameter × 9 mm height) were injection moulded in an Arburg 221K 350-100 machine. Green parts were solvent debinded in acetone at 35°C for 40h, then thermal debinded and dehydrided at 450°C for 2h under argon, and finally sintered at 1000°C for 4h under argon in a Nabertherm VHT08-16MO MIM furnace (Fig. 2). The density was measured by the Archimedes method and gas pycnometry. Compression tests were performed using a Zwick 1475 machine.
RESULTS: Fig. 3 shows the cross section and the
interconnected porosity of a sintered part. The porosity is 50 vol.% (27 vol.% open and 23 vol.% closed). The pore size is between 100 and 500 µm. Compressive strength values determined at 0.2% and 50% strain are 146 MPa and 610 MPa
respectively. The Young’ modulus is about 12 GPa (Fig. 4).
Fig. 2: Green and sintered porous titanium parts.
Fig. 3: Microstructure of sintered PIM titanium. Scale bars are 1mm (left) and 100 µm (right).
Fig. 4: Compression behaviour.
DISCUSSION & CONCLUSIONS: Open
porosity and interconnection diameters could be optimized by varying the space holder volume fraction and sintering conditions. Porous titanium parts have been processed by a novel route from low cost TiH2 base powder.
REFERENCES: 1 T. Imwinkelried (2007), J.
Biomed. Mater. Res. A, 81 (4): 964-970. 2 A. Bansiddhi, D. C. Dunand (2008), Acta Biomater.,
4:1996-2007. 3 M. Köhl, T. Habijan, M. Bram,
H.-P. Buchkremer, D. Stöver and M. Köller (2009),
Adv. Eng. Mater., 11 (12): 959-968. 4 E. Carreño-Morelli, J.-E. Bidaux, M. Rodriguez-Arbaizar, H. Girard and H. Hamdan, Proc. of EuroPM2011, Barcelona, Spain, October 9-12, 2011, 2:105-110.
ACKNOWLEDGEMENTS: This project was
funded by HES-SO under a MaCHoP 06-11 grant and the Erasmus Programme. The technical support of H. Girard is gratefully acknowledged.
