Evaluation of the quality of layers applied by LDT laser metal deposition

The article presents the results of a study of C45 carbon steel hardfacing using laser metal deposition with Stellit Co-21 powder. The microstructure of the cross-section of samples prepared with different scanning speed and the amount of used powder at constant laser power was observed. Analyzing the cross-sectional areas of the samples, it was found that, at specific production parameters, cracks occur in weld overlay, which should be associated with the amount of heat supplied and discharged, especially at the unheated basis.This may be confirmed by the presence of deposits of weakly branched dendrites in the microstructure, which should be related to the directional heat dissipation process and rapid directional crystallization. It is possible to regulate these phenomena by selecting appropriate processing parameters. The microstructure analysis of cross-sectional areas of samples after hardfacing using LDT technique indicates good metallurgical quality of the deposit with a small heat affected zone of about 660÷760m. The microhardness measurements on the sample cross-sections indicated a wide micohardness distribution ranging from 510HV1 in the weld overlay, about 410HV1 in the heat affected zone, to 270HV1 in the C45 steel base.