SOLIDIFICATION STRUCTURE AND ABRASION RESISTANCE OF HIGH CHROMIUM WHITE IRONS

Superior abrasive wear resistance, combined with relatively low produc tion costs, makes high Cr white cast irons (WCIs) particularly attract ive for applications in the grinding, milling, and pumping apparatus u sed to process hard materials. Hypoeutectic, eutectic, and hypereutect ic cast iron compositions, containing either 15 or 26 wt pct chromium, were studied with respect to the macrostructural transitions of the c astings, solidification paths, and resulting microstructures when pour ed with varying superheats. Completely equiaxed macrostructures were p roduced in thick section castings with slightly hypereutectic composit ions. High-stress abrasive wear tests were then performed on the vario us alloys to examine the influence of both macrostructure and microstr ucture on wear resistance. Results indicated that the alloys with a pr imarily austenitic matrix had a higher abrasion resistance than simila r alloys with a pearlitic/bainitic matrix. Improvement in abrasion res istance was partially attributed to the ability of the austenite to tr ansform to martensite at the wear surface during the abrasion process.