Technical Paper: PIM International, Vol.1 No. 4 December 2007, pages 60-62, 960 words

Authors: Rudolf Zauner and Michael Scheerer

Austrian Research Centers GmbH - ARC

Abstract

316 L (DIN1.4404) is known to be the most commonly used material in metal injection moulding. In search for new applications for MIM, the material DIN 1.4404 has been tested for its mechanical properties under liquid hydrogen conditions (-253C). Tensile bars and impact strength test bars were injection moulded and sintered to different porosities and the material testing performed under room temperature, liquid nitrogen (-196C) and liquid helium (-269C) temperatures. For the fully dense samples it was shown that at room temperature an Rm of around 550 MPa and a ductility of 55%, at liquid nitrogen temperature an Rm of around 1350 MPa and a ductility of 38% and at liquid helium temperature an Rm of around 1500 MPa and a ductility of 22% could be achieved, showing impressively the increase in strength at cost of ductility at low temperatures. Additional characterisation data – including non destructive testing (NDT) data - of impact experiments at room temperature and liquid nitrogen temperature will be presented.

Introduction

Gaseous hydrogen has the highest energy content of any common fuel by weight (about three times more than petrol), but a very low energy content by volume (about four times less than petrol). However, hydrogen also exists in a liquid state, but only at extremely cold temperatures, leading to an excellent energy content by volume. Liquid hydrogen typically has to be stored at 20 Kelvin or -253C. The storage tanks are insulated, to preserve temperature, and reinforced to store the liquid hydrogen under pressure. Research in the field of liquid hydrogen storage centres around the development of new tank materials, resulting in lighter, stronger tanks, and improved methods for liquefying hydrogen. Another field of research is the introduction of net-shape technologies such as powder injection moulding (PIM) for the production of functional components for liquid hydrogen storage tanks. In this work, 316 L PIM components have been tested and characterised......

Further sections of this article include:

- Experiments

- Characterisation

- Characterisation at room temperature

- Temperature-dependent mechanical properties

- Charpy Impact tests at LN2 (-196°C) on PIM and conventionally manufactured material

- Outlook

Figures and Tables:

Fig. 1 Tensile and three point bend bars of material DIN 1.4404 (green parts)

Fig. 2a Vacuum sintering furnace

Fig. 2b Sintered tensile bars of material DIN 1.4404

Fig. 3 Arrangement for tensile testing at 4.2 K in LHe featuring the 4-column testing machine, the LHe – cryostat containing the specimen (black cylindrical object) and the storage container to the right side

Fig. 4 Measurements of elastic modulus

Fig. 5 Influence of the sinter temperature on the elastic properties

Fig. 6 Influence of the sinter temperature on the mechanical properties

Fig. 7 Comparison of mechanical data at different temperatures

Fig. 8 Colour coded amplitude of the back wall echo

Fig. 9 Average amplitude of the back wall echo

Fig. 10 Results of the charpy impact tests