LASER CLADDING OF A COBALT-BASED ALLOY - PROCESSING PARAMETERS AND MICROSTRUCTURE

Laser cladding experiments with a hypoeutectic Stellite 6 alloy were carried out with a low (1.67 mm/s), an intermediate (13.3 mm/s) and a very high (167 mm/s) scanning speed in order to examine the influence of the processing conditions on the type, size and fraction of phases present. Altering the scanning speed over two orders of magnitude led to a marked decrease in the microstructural size. With the fast processing conditions, the fraction of interdendritic eutectic was also decreased. The results are discussed based on a recent dendritic growth model for multicomponent alloys, using the solidification conditions deduced from a two-dimensional (2D) heat flux model and the phase diagram parameters determined with numerical calculations of the quaternary Co Cr-C-W phase diagram.