Erosion of aluminium-based claddings on steel by sand in water

This paper describes the slurry erosion of a range of HVOF deposited alumin ium-based claddings on steel by sand in water. Coatings, approximately 300 mum thick, of commercially pure aluminium, eutectic aluminium/silicon alloy (12%) and of a novel composite incorporating alumina in this alloy have be en tested, both as sprayed and as ground to remove surface roughness as far as possible. Angular silica sand of mean diameter 235 mum was used at a co ncentration of 2.5% in tapwater at impingement angles of 90 degrees and 30 degrees and a jet velocity of 27 m/s. Mass loss data and surface structure, as shown by electron microscopy and profilometry, are related to the test conditions, initial surface topography, material hardness and microstructur e, especially porosity. They are discussed in terms of the mechanisms of er osion that occur in the different materials, with reference to microcutting and plastic deformation of the surface and to the effects of the alumina i nclusions. The consequences of poor flow-out, leading to significant residu al porosity of the composite cladding are discussed. (C) 2001 Elsevier Scie nce B.V. All rights reserved.