Effect of Cr2O3 and WO3 Addition on Pore Formation and Microstructure in Iron Foam

Abstract

Iron-based metal foam has several advantages over aluminum alloy foam, such as high strength and low cost. However, iron foam does not have high porosity and uniform pore size. It is known that both the decrease in the interfacial tension between molten iron and pores and the increase in the viscosity of the melt contribute to the stabilization of pores. The objective of this study is to investigate the effect of the addition of chromium and tungsten oxide (Cr2O3 and WO3) powders, which are expected to act as stabilizers, on the porosity and pore size of iron foam. Blended powders of pure iron, 3.0 mass% graphite, 0.5 mass% Fe2O3, and a certain amount of additives were compacted. The additives used were Cr2O3 and WO3, whose composition ranged from 0.0 to 5.0 vol%. The porosity and the average pore size of the iron foam were measured after heating the precursor at 1563 K. The porosity decreased slightly with increasing additive content. Although the addition of Cr2O3 and WO3 powders led to a decrease in the pore size, the amount of additives did not affect the average pore size. The addition of Cr2O3 particles to the precursor led to the formation of a Cr2O3 layer on the pore surface of the iron foam and a change in microstructure of the obtained iron foam. On the other hand, the addition of WO3 particles did not result in the formation of a WO3 layer on the pore surface.