Forming conditions of iron-disilicide by slip casting

Optimal slip conditions for molding of iron-disilicide were determined. The chemical compositions of the starting material were Fe0.91Mn0.09Si2 and Fe 0.98Co0.02Si2 The mean particle diameters of both kinds of powder were appr oximately 6 mum. The slip were prepared by adding distilled water to the po wder, then, the hydrogen exponent (= pH) of the slips was controlled by add ing 3% aqua ammonia. Ammonium alginate was used as a deflocculant as well a s a binder. When the pH was greater than 7 for the Fe0.98Co0.02Si2 slip and greater than 8.5 for the Fe0.91Mn0.09Si2 slip, the apparent viscosity was low enough to enable casting, The pHs of the Fe0.98Co0.02Si2 slip and the F e0.91Mn0.09Si2 slip were determined to be 7 and 8.5, respectively, because a higher pH slip corroded the plaster faster. Although the apparent viscosi ty increased with the powder concentration, castability was satisfied and t he density of the sintered specimen did not depend on the powder concentrat ion under the slip and sintering conditions of this study. Accordingly, the powder concentration was determined to be 77%, because the apparent viscos ity of the slip was the lowest at this concentration. The shrinkage of the specimen before and after sintering was 17.1 +/- 0.3% and was independent o f both the powder concentration and starting material. The ammonium alginat e provided stability to the slip and improved the strength of the green bod y.