Additive manufacturing of stellite 6 superalloy by direct laser metal deposition – Part 2: Effects of scanning pattern and laser power reduction in differrent layers

In this study, the purpose is to investigate two strategies for direct laser metal deposition method (DLMD) additive manufacturing of stellite 6 Cobalt-based superalloy experimentally. The first one was the effect of scanning pattern, and the second one was the influence of laser power reduction in different layers in additive manufacturing (AM). For the experiments a coaxial nozzle head coupled with a 1 kW continuous fiber laser was used. This research aim was to examine the effect of these two strategies on characteristics of the additive manufactured components. The macro section of the geometrical dimensions, including height and width, profiles of microhardness, grain size, and microstructure of the 3D printed wall samples were investigated. The height stability of samples was also examined. The results indicated that scanning pattern has an important role in all the additive manufactured components features. Results show that when the unidirectional scanning pattern was used, the more stability will be obtained. The average grain size of samples which were produced by unidirectional scanning pattern and bidirectional scanning pattern was 2.25 μm and 2.83 μm, respectively. The trend of changes in the grain size of the samples shows that the beginning and the end of the LAMed wall are larger than the sample's center, and the trend of the microhardness variation is in reverse regime of the grain size. Also, it was shown that with decreasing the laser power from the substrate upwards, the width of samples has reduced.