INTERACTION OF SILICON NITRIDE AND METAL SURFACES

An Mn-Fe-rich slag forms near the tips of Si3N4-based indexible cutting tools during the machining of cast iron. Manganese and iron were found to react chemically with Si3N4 to form a liquid phase in the presence of air, but not in the absence of air, at temperatures comparable to those reached during machining operations. Thus, chemical reactions between Fe, Mn, Si3N4, and O2 may be a factor in the wear of Si3N4 tools against cast iron.