Influence of tungsten carbide particle size and distribution on the wear resistance of laser clad WC/Ni coatings

Thick composite coatings of carbides (e.g. WC) in a metal matrix are ideal for components subject to heavy abrasive wear. An emerging deposition technique for such wear resistant cemented carbide coatings is laser cladding. This technique has, contrary to surface welding and spraying methods, the potential to coat very locally and on highly complex components. Adhesion and damage resistance is also improved by laser cladding. In this paper the influence of carbide particle size and distribution on the wear resistance of laser clad coatings is discussed. A nickel based matrix reinforced with WC/W2C carbides is deposited by a CO2 laser on low carbon steel substrates. Different coatings are made with three different particle sizes of the carbides and volume fractions ranging from 0 up to 50%. Three different wear modes are evaluated. First, ball-on-disc tests with an Al2O3 ball have been performed. The ball cratering test with 4 mum SiC abrasive is used to assess mild abrasive wear. Finally, the resistance against severe two body abrasion is tested in a pin-on-disc test. A clear dependency of the wear resistance on the carbide concentration is found, which is more pronounced for the coatings with the finest WC/W2C carbides. The magnitude of the decrease in wear however is highly dependent on the wear mode. In two body abrasion and in the sliding wear, a small amount of carbides is sufficient to improve the wear resistance drastically. Other coating characteristics such as microstructure, hardness and internal stress are assessed. (C) 2004 Elsevier B.V. All rights reserved.