THE MATRIX CORROSION OF TUNGSTEN CARBIDE CARBON-STEEL METAL-MATRIX COMPOSITES

Metal matrix composites (MMCs) have been prepared by melting in an arg on are two high carbon tool steels in the presence of particles of fus ed tungsten carbide. The microstructures were examined using scanning electron microscopy (SEM) and energy dispersive analysis (EDA). The co rrosion characteristics were ascertained in both acidic and alkaline e nvironments by potentiodynamic polarisation. SEM showed that the tungs ten carbide collects mainly along the grain boundaries where it appear s as dendritic-like deposits. The tungsten is present as iron tungsten carbide, Fe3W3C. The polarisation studies, in conjunction with SEM, s howed that in acid environments the MMC is susceptible to general corr osion along the grain boundaries. However, in aerated alkaline corrode nts containing aggressive chloride ions, spontaneous passivation will occur followed by pitting corrosion of the iron-rich grains. (C) 1997 Elsevier Science Ltd.