Abstract: An erosion resistant article is formed by cladding a substrate with tiles having a surface layer of polycrystalline material such as diamond or cubic boron nitride. The tiles may be entirely polycrystalline diamond or may have a backing of cemented tungsten carbide. Such an article can be trim for a high pressure valve wherein a sleeve is partly lined with polycrystalline diamond tiles and a plug is clad with polycrystalline diamond tiles.