MODELING OF CHEMICAL WEAR IN FERROUS-ALLOYS SILICON-NITRIDE CONTACTS DURING HIGH-SPEED CUTTING

The wear resistance of Si3N4 in machining of iron alloys can be surpri singly low due to chemical affinity for dissolution in the metal. This limits the use of Si3N4 inserts in high speed machining of steels, wh ile Si3N4 retains the best performance of all cutting materials in tur ning of grey cast iron, a different ferrous alloy. The chemical wear o f several ceramics has been investigated on the basis of dissolution i n pure iron by Kramer and Sub. Nevertheless, the influence of alloy el ements was not studied. In the present work, solid solution thermodyna mics is applied to predict chemical wear of Si3N4 by Setting the influ ence of interaction coefficients of the alloy elements in the Henrian activity of Si and N in austenite. The model predicts the relative ord er of magnitude of the crater wear of Si3N4 inserts in machining of to ol steels, carbon steels and grey cast iron. (C) 1998 Acta Metallurgic a Inc.