Scouring erosion resistance of metallic materials used in slurry pump service

Abstract

Low impact angle erosion resistance is a critical requirement of materials used in pumps, piping, valves, nozzles, cyclones and other components which transport and process most mineral slurries. The Coriolis method offers a suitable technique for assessing behavior under such scouring attack conditions. It is being used increasingly in support of the mining/mineral processing industry, to compare and discriminate between candidate materials and also assist in the development of new products and protection systems. The specific method used in the current study involves high velocity erosion with aqueous slurry containing 10 wt.% of AFS 50-70 silica test sand. This compares reasonably with the main, extremely abrasive solids constituent encountered in mining and processing oil sands deposits in northern Alberta, Canada. These are becoming a rapidly growing and critically important source of oil in North America. Abrasion resistant chrome white iron castings typically covered by the ASTM A532 standard, are used widely in slurry pump components particularly in oil sand operations. However, the development of proprietary cast hypereutectic chromium white irons with microstructures containing primary M 7C 3-type carbides, is providing the capability to significantly improve the wear performance of such parts. In certain applications where corrosion contributes significantly to overall attack, lower carbon and higher chromium-bearing variants are employed. A comparison of the Coriolis erosion behavior of a wide range of commercially available cast wear and corrosion resistant and high toughness alloys used in pump manufacture, has confirmed anticipated performance ranking and the superiority of the latest generation of hypereutectic chrome white irons. The ameliorative influence on scouring erosion behavior of high carbon content, hardness and carbide volume fraction and particularly of fine carbide size has been demonstrated. A correlation is drawn between test data and service performance.