Abstract
Nickel based and cobalt based hardfacing layers produced by laser and a variety of conventional welding and spraying processes have been compared. Parameters measured include dilution, distortion, microstructure, surface texture, wear resistance, and macro- and microhardness of the constituent phases. Laser processing was found to give the lowest variation in deposit thickness, together with a fusion bond of low dilution. The high cooling rates of laser deposits lead to finer structures, greater microhardness, and enhanced solid solubility (offering the opportunity of developing a new range of hardfacing alloys). Carbide and eutectic phases in the laser deposited layers were of constant composition, whereas the solid solution phase was the hardest obtained owing to the presence of higher concentrations of carbon and chromium. Abrasive wear tests in general showed improved properties with increasing carbide size, although the increased hardness of the laser layer solid solution phase was also of benefit. The cobalt based laser hardfaced layer showed the highest wear resistance.
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