Morphology and characterization of laser clad composite NiCrBSi-WC coatings on stainless steel

In this work, several mixtures of self-fluxing NiCrBSi alloy powder and a nickel-clad WC powder (10 wt.% Ni and balance WC) were laser cladded on stainless steel substrates of austenitic type (AISI 304). The aim of the study was to determine the influence of the volume fraction of the reinforced WC particles on the formation and performance of the composite layer. The effect of other parameters of the treatment, such as the laser energy, beam profile, traverse speed and the mass rate of the feed powder was also investigated. Clad layers of 0.5-1.5 mm height were obtained, its microhardness measured and the microscopic morphology and distribution of tungsten carbide particles within the layer characterized by scanning electron microscopy (SEM). It was found that most clad layer properties such as its porosity, microhardness and homogeneity are determined by the percentage of WC particles in the mixture. Pores were observed for volume fractions roughly above 50%. Below this limit, homogeneous, dense and crack free clad layers were obtained, with measured hardness ranging between 600 and 1000 HV depending on the WC content. (c) 2005 Elsevier B.V. All rights reserved.