Effect of slurry composition on the microstructure and mechanical properties of SS316L open-cell foam

This experimental study systematically examines the effect of slurry composition on the microstructure and mechanical properties of open-cell foams, by altering the binder concentration and powder loading of SS316L slurries used in the template replication foam fabrication. The slurry and foam morphologies were observed by Scanning Electron Microscopy (SEM), whereas the rheological properties of the slurry were obtained using a rotational viscometer and parallel plate rheometer. Foam strut densities were measured by a gas pycnometer, which subsequently allowed for the calculation of foam porosity. The mechanical behaviours of the foams were attained through compression test. Results show that increasing both binder and powder contents lead to an increase in slurry viscosity, foam bulk density, green strut density and mechanical strength. A process window for foam fabrication was also proposed based on macroscopic foam morphology, rheological and mechanical properties, and corrosion behaviour of the resulting SS316L foams. Based on the proposed process window, the binder concentration is suggested to be within 10 vol% and 14 vol% and powder loading within Φ = 0.75 and 0.80. This study demonstrates that the microstructure of foam produced by the template replication method can be well-controlled by optimising the composition of the slurry, which is able to attain a higher compression strength than that in the conventional range of Gibson and Ashby scaling law.