Technical Paper: PIM International, Vol.2 No. 3 September 2008, pages 60-63, 1868 words

Authors: Kazuaki Nishiyabu [1], Satoru Matsuzaki [2] and Shigeo Tanaka [2]

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

Abstract

A production method for micro-porous metal components has been developed by applying the powder space holder (PSH) method to metal powder injection moulding (MIM) process. This paper deals with the liquid infiltration property of micro-porous metals produced by the PSH method. The material used is high-corrosion resistant austenitic stainless steel 316L, and the samples have micro-sized open porous structures with high specific surface area. The test apparatus for evaluating a liquid infiltration performance of the porous specimens was developed using analytical balance. From the weight change in a liquid infiltration test, the effecting factors on water absorption behaviour of the porous specimens were revealed. The results of the infiltration rate were compared to some important characteristics of the porous specimens such as mean pore diameter, liquid and gas permeability and specific surface area measured by capillary flow porometry. The effects of pore size on the infiltration rate were seen between porous specimens with a single digit µm and 15µm in mean constricted pore diameter..

Introduction

According to R.M.German’s textbook on powder metallurgy (P/M) [1], it is described that a natural application for P/M is in the fabrication of controlled pore structures for bearings, filters, flow restrictors, sound absorbers, heat pipes, and biomedical implants . Pore size control is achieved by classifying the powder into a narrow size fraction with controlled densification during processing. Therefore, there is no doubt that the pore structure manipulation is the key reason for selecting a P/M approach to fabricating porous metals. Generally speaking on pore size, a sintering approach is easier to make small pores than foaming or deposition methods [2].

In porous metals which have been manufactured by traditional P/M, however, the combination of pore size and porosity is limited, i.e. a single digit micron-size and sub-micron size porous structures in holding high porosity have not been produced sufficiently. Particularly the pore is interglobular interstice whose shape is not ideal because of notch acuity and also high resistance of a fluid to flow......

Further sections of this article include:

- Production of micro-porous metals
- Principle and evaluation
- Materials and experimental
- Results and discussion
- Conclusions
- References

Figures and Tables:

Fig. 1 Powder space holder method for producing micro-porous metals

Fig. 2 Schematic of apparatus used for evaluating the liquid infiltration performance of porous specimens

Fig. 3 SEM images of porous specimens.

Fig. 4 Pore size distributions of porous specimens.

Fig. 5 Typical behavior of weight change during immersion of porous specimens (3-10, l=7.5mm)

Fig. 6 Effects of immersion length on weight change (Specimen 3-10)

Fig. 7 Saturation time versus immersion length

Fig. 8 Effects of surface treatment on weight change (Specimen 3-10, l=7.5mm)

Fig. 9 Effects of pore size on weight change (l=7.5mm).

Table 1 Properties of porous specimens

Table 2 Effects of acid cleaning (3-10, l=7.5mm)

Table 3 Effects of immersion length and pore size on infiltration rate (á) and infiltration percentage (Va)