Study of carbide dissolution into the matrix during laser cladding of carbon steel plate with tungsten carbides-stellite powders

High power diode laser with coaxial powder injection was used to deposit single tracks of cobalt alloys with tungsten carbides on to a carbon steel plate in order to study carbide dissolution in the metallic matrix. Two kinds of cobalt alloy powders (Stellite 12 and Stellite 21) having different content of tungsten and carbon were used. Processing parameters were changed to obtain different cladding conditions, and effect of substrate preheating was evaluated too. Carbides dissolution, measured with image analysis and EDXS analysis, increases with the increase in the laser power. A low carbon and the absence of tungsten in the matrix powder promote carbides dissolution. Substrate preheating also leads to a higher dissolution. Matrix microhardness of the Stellite 21 increases with the increase in carbides dissolution, while matrix microhardness of the Stellite 12 does not change. Hardness of the coatings is slightly influenced by the dissolution phenomena.