Influence of powder particle size distribution on rheological properties of 316 L powder injection moulding feedstocks

• Published in: Powder technology 2010-06, Vol.200 (1), p.30-36
• Main Authors: Sotomayor, M.E., Várez, A., Levenfeld, B.
• Format: Article
• Language: English
• Subjects: 316 L stainless steel; Applied sciences; Chemical engineering; Exact sciences and technology; Injection moulding; Miscellaneous; Particle size distribution; Rheological properties; Solid-solid systems
• ISSN: 0032-5910; 1873-328X
• DOI: 10.1016/j.powtec.2010.02.003

The rheological behaviour of highly filled polymer systems used in powder injection moulding (PIM) technology influences strongly the final properties of the products. The study of the influence of particle size distribution on the rheological properties of 316 L stainless steel feedstocks is presented. Two kinds of gas-atomized powders were employed with d 90 of 8 and 26 μm of particle size. Five feedstocks were prepared at powder loadings of 50, 55, 60 and 65 vol.%, employing both starting powders and their own mixtures in volume ratios 25/75, 50/50 and 75/25. The binder was composed by 50 vol.% of high density polyethylene and 50 vol.% of paraffin wax. Feedstocks were prepared in a torque rheometer with a pair of roller rotor blades and rheological measurements were performed in a capillary rheometer. The effects of the powder loading and different particle size distributions on the rheological properties of feedstocks were investigated. Different rheological parameters, like melt viscosity, power flow index and activation energy were determined. A relationship between powder characteristics and rheological behaviour was established. There are several papers about injection moulding of stainless steels but the influence of particle size distribution and powder loading on the rheological behaviour of feedstock has not been deeply investigated. In this work the influence of powder particle size distribution of 316 L feedstocks on rheological properties has been determined. The rheological behaviour of this kind of systems depends strongly on the powder particle size and is crucial to achieve a successful powder injection moulding process. [Display omitted]