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.