Stainless steel hollow fibres – Sintering, morphology and mechanical properties

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This work investigates the effects of the sintering conditions on the morphology and mechanical performance of stainless steel (SS) hollow fibres. It was found that the morphology of the green hollow fibre to a large extent predetermines the final morphology of the sintered hollow fibre. There is a set of conditions which produce hollow fibres with high mechanical strength over 1000MPa such as using small SS particles (6 and 10μm), PEI as the polymeric binder and minimal amounts of the viscosity modifier PVP (preferably close to 0wt%), particle loadings higher than 50wt%, and sintering temperatures between 1050 and 1100°C. The ductility of the hollow fibres was not greatly affected by these parameters as flexural strain variations were very small, though sintering in argon resulted in the formation of a few larger pores which tended to propagate cracks, leading to lower flexural strain. The sintering process in inert gases resulted in mass transfer of residual carbon from the binder to the SS particle, leading to regions of rich and lean chromium carbides, though mechanical effects of these inclusions were not significant. Finally, the morphology played a major role as SS hollow fibres containing a higher volume of sponge-like region were mechanically stronger than the analogous fibres dominated by finger-like and macroporous regions.