| Metal matrix composites (MMC) can be applied to steel substrates as wear coatings. MMC's consist of a reinforcing phase combined with a tough metal matrix. The behaviour of two nickel MMC's is investigated: Ni-WC and Ni-B 4C. Experiments were designed and carried out where WC or B4C were added to molten Ni. The melt was sampled following the addition of the ceramic. Analysis techniques included chemical analysis, optical microscopy, electron microprobe microanalysis and x-ray diffraction. In the Ni-WC system a portion of WC reacted, dissolving W in the nickel. Reactions in the Ni-B 4C system produced nickel-borides. A thermodynamic analysis of the systems was also completed. The Ni-WC thermodynamics supported the experimental results. The Ni-B4C thermodynamics was also in agreement with the experimental results in all but one case. The thermodynamic analysis also explored the use of Cr, Mn and Cu as matrix materials. This analysis suggested that Cu might be suitable in a Cu-Ni alloy. |
