WEAR BEHAVIOR OF RAPIDLY SOLIDIFIED FE68CR18MO2B12 ALLOYS

The sliding wear behaviour of a range of rapidly solidified alloy samp les based on the composition Fe68Cr18Mo2B12 and prepared by planar-flo w casting have been evaluated using a modified crossed-cylinder wear t esting 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 amorpho us state and after devitrification at various temperatures, and a bulk devitrified sample prepared by hot extrusion of the crushed ribbon wa s also investigated. Low-temperature crystallization of the ribbon pro duced a high volume fraction of metastable Fe3B in a ferritic matrix, whilst high-temperature crystallization produced M2B and Mo-rich borid es, again in a ferrite matrix. Results from the wear tests showed that the alloy having the stable M2B and Mo-rich borides exhibited the bes t wear performance and that the amorphous material exhibited the highe st wear rate, whilst the alloy having Fe3B precipitates gave intermedi ate rates of wear. The reasons for the differences in wear behaviour a re discussed in relation to the stability and scale of the microstruct ure. The wear mechanisms, which were essentially mild, are also discus sed.