Technical Paper: PIM International, Vol.3 No. 1 March 2009, pages 60-63, 1939 words

Author: Kazuaki Nishiyabu [1], Satoru Matsuzaki [2] & Shigeo Tanaka [2]

[1] Osaka Prefectural College of Technology, 26-12 Saiwai, Neyagawa 572-8572, Osaka, Japan
[2] Taisei-Kogyo Co., Ltd., 26-1 Ikeda-kita, Neyagawa 572-0073, Osaka, Japan

Abstract

Metal powder injection moulding (MIM) is a promising net-shape manufacturing method for porous metal components with high dimensional accuracy and 3 dimensional complicated shapes, which are required in several highly functional applications. Powder space holder (PSH) method is capable of fabricating the controlled pore structures the pore size and can be changed from sub-microns to a few hundred microns, and porosity from 0% to around 80% in volume.

In this study, pure titanium was chose for experiments as the representative materials of medical implants. The aim of this study is to demonstrate the feasibility and effectiveness of MIM process in producing the multilayered porous metal components. The thick-walled cylindrical pipe structures with three layers of various porosities were moulded by sequential injection moulding, and sintered by co-bonding. The pore formation and some physical properties of sintered porous specimens produced using porous compounds with various fractions of space holding particle were investigated. It was confirmed that the method proposed in this study was useful in producing the metal components with micro-sized pores and multi-layered structures..

Introduction

The possibility of dental implants for functionally disordered hard tissues like bone and teeth have received a lot of attention recently in addition to substituting the hard tissue instrumentations like artificial bones, artificial hip joints and artificial teeth. Pure titanium (Ti) has been the most widely used for orthopedic implant material to date because of its excellent combination of biocompatibility, corrosion resistance for acidum, salt water, blood and mechanical properties, such as low specific gravity and high strength [1-3]. However, Young’s modulus of pure Ti (110GPa) is much higher than that of human bone (12-23GPa). Critical problems caused by the mismatch of elastic modulus between implant and human bone are still unsolved. One way to alleviate the problems is, therefore, to reduce Young’s modulus of pure Ti by introducing pores, thereby minimising damage to tissues adjacent to the implant and eventually prolonging the device life time. According to [1], sintered porous Ti compacts having Young’s modulus close to that of human bone has been developed. The porous compacts having porosity of 19-35vol.% were fabricated using pure Ti powder with 300-500ìm in particle sizes. Also, in [2] porosity-graded Ti.......

Further sections of this article include:

- Production of multilayered micro-porous metals
- Experimental details
- Results and discussion
- Conclusion

Figures and Tables:

Fig. 1 Process flow of powder space holder method for micro-porous metals
Fig. 2 Sequential injection moulding method
Fig. 3 Pore size distribution of sintered porous Ti disk (65vol.% PMMA)
Fig. 4 Flow behaviors of sintered porous Ti disk (65vol.% PMMA)
Fig. 5 Surface structures of single-layered porous Ti pipes with various fraction of PMMA particle
Fig. 6 Surface structure of multilayered porous Ti pipe (65-30-0)
Fig. 7 Porosity of sintered porous Ti as a function of fraction of PMMA particle
Fig. 8 Compressive stress vs. strain curves of single-layered and multilayered (65-30-0) porous Ti pipes (h/d=1.5)
Fig. 9 Fracture states of single-layered and multilayered porous Ti pipes after compression test
Fig. 10 Compressive stress vs. strain curves of multilayered porous Ti pipes with various aspect ratios of height to diameter (h/d)
Fig. 11 Overviews of Ti micro impeller with porous structure

Table 1 Experimental materials and fraction of constituents
Table 2 Physical properties of sintered porous Ti disk (65vol.% PMMA)