WEAR BEHAVIOR OF RAPIDLY SOLIDIFIED FE68CR18MO2B12 ALLOYS

The sliding wear behaviour of a range of rapidly solidified alloy samples based on the composition Fe68Cr18Mo2B12 and prepared by planar-flow casting have been evaluated using a modified crossed-cylinder wear testing rig with a cobalt-bonded tungsten carbide counterface. A range of microstructures was investigated and the effect on wear performance evaluated. Alloys in ribbon form were examined in the as-cast amorphous state and after devitrification at various temperatures, and a bulk devitrified sample prepared by hot extrusion of the crushed ribbon was also investigated. Low-temperature crystallization of the ribbon produced a high volume fraction of metastable Fe3B in a ferritic matrix, whilst high-temperature crystallization produced M2B and Mo-rich borides, again in a ferrite matrix. Results from the wear tests showed that the alloy having the stable M2B and Mo-rich borides exhibited the best wear performance and that the amorphous material exhibited the highest wear rate, whilst the alloy having Fe3B precipitates gave intermediate rates of wear. The reasons for the differences in wear behaviour are discussed in relation to the stability and scale of the microstructure. The wear mechanisms, which were essentially mild, are also discussed.