Microstructural characterization and wear behavior of laser cladded nickel-based and tungsten carbide composite coatings

Laser cladded nickel-based and tungsten carbide WO composite coatings were produced by varying laser beam power and were characterized by scanning electron microscopy. Microstructure of the clad layer is greatly affected by the processing parameters. The layer produced under the optimized processing conditions had uniform structure and excellent bonding with the substrate and was free of pores and cracks. Due to the right selection of the laser processing parameters, WC particulates partially dissolved, with the epitaxially grown dendrites around them, combined strongly with the coating materials and well-distributed in the layer. The larger the laser beam power is, the higher level of the dissolution of WC phase in metal matrix is, and the more WC particles tended to sink to the bottom of the layer. The wear test results show that the composite coating with WC hard phases has improved wear resistance when compared with the Ni-based alloy coating. The wear mechanism of the specimens is discussed based on microscopic observation of the worn surface and wear scraps. (C) 2002 Elsevier Science B.V. All rights reserved.