Explaining microstructural and physical variations in rapid additive manufactured waspaloy parts through the laser-deposition thermal cycle

Laser direct metal deposition has the potential to increase the material efficiency during the manufacture of superalloy aerospace components and also to reduce the need for welded joints to produce the necessary geometries. However, a possible problem is inconsistent microstructure, and therefore physical properties, in the deposited part. In this work, the factors that affect microstructure formation and evolution were examined in simple Waspaloy parts deposited using a high power diode laser and coaxial powder nozzle across a range of process parameters. Thermal imaging and embedded thermocouples were used to record the thermal cycle during deposition at different positions within the part and this is correlated with the wall characteristics and the final microstructures formed. Results allow the extent of the variations in sample properties with process parameters and position to be determined and indicate that intra melt pool factors such as local fluctuations in temperature gradients due to Marangoni flow and changes in nucleation density due to injected powder are significant.