FACTORS AFFECTING PRESSURE INFILTRATION OF PACKED SIC PARTICULATES BY LIQUID ALUMINUM

Pressure infiltration is being currently used to evaluate the wettability of ceramic particles and fibers by liquid metals. The objective of this work is to investigate the effect of type and surface condition of the particulates and infiltration atmosphere on pressure infiltration of packed SiC particulates by pure liquid aluminum. Fourteen SiC particulates from five different suppliers, of green (high purity) and black (low purity) types, were used. Two of the particulates were subjected to either low- or high-temperature heat treatments in order to either burn organic residues or promote oxidation. Infiltrations were carried out in air, argon, argon/hydrogen, and nitrogen/hydrogen atmospheres. The results indicate that the threshold pressure does not depend appreciably on the type of particulate. A heat treatment at 600 degrees C improves the infiltration performance of particulates having a large amount of organic residues, whereas oxidation at 1000 degrees C decreases the threshold pressure. The results also illustrate the effects of the infiltration atmosphere; in particular, it is shown that inert or reducing atmospheres improve wettability.