Microstructure evolution of laser clad layers of W–C–Co alloy powders

Clad layers using high power carbon dioxide laser and various powder compositions of W, C, Co and WC on carbon steel substrate have been investigated. Microstructures of the clad layers are greatly affected by the processing parameters: powder size; powder type; shielding gas; degree of dilution; and geometry of the clad layer. Clad layers with large WC particles in a eutectic matrix and a high hardness, or with a mostly eutectic structure and low hardness, can be made for applications of cutting tools or wear resistant surfaces, respectively. Microstructure such as: (1) WC, Co3W3C, and a binary eutectic mixture of Co3W3C and α-(Fe,Co); (2) Co3W3C and a binary eutectic mixture of Co3W3C and α′-(Fe,Co); (3) a binary eutectic mixture of Co3W3C and α′-(Fe,Co) have been produced in the clad layer.