SOLID-STATE REACTIONS BETWEEN SILICON-CARBIDE AND (FE, NI, CR)-ALLOYS - REACTION PATHS, KINETICS AND MORPHOLOGY

Solid state reactions between silicon carbide and various (Fe, Cr, Ni)-alloy compositions are studied. The different phases present in the reaction scale, their chemical composition and morphology are determined. The reaction path and the reaction kinetics are also measured. A typical composition distribution and morphology of the reaction scale is associated to each alloy element: iron yields broad alpha-iron zones with randomly distributed graphite precipitates; the presence of nickel results in typical reaction scales made of alternating bands of pure silicide and of other bands of silicide containing a high density of carbon precipitates; chromium leads to large chromium carbide precipitates on the alloy side. The solid state reactions between SiC and (Fe, Cr, Ni)-alloys can be described as the dissolution of silicon carbide by iron and nickel, resulting in the formation of silicon-rich compounds (alpha-, tau-phase, Ni5Si2 or Ni2Si) and in the precipitation of graphite flakes.