Substrate influence in laser blown powder of nickel superalloys

A major challenge with productionizing Laser Blown Powder manufacturing processes is developing robust process control methods to verify material quality. Laser deposited structures are sensitive to the underlying substrate, including its chemistry, thermal properties, geometry, surface roughness, appearance, etc. It is therefore challenging in many applications to ensure that the deposited material produced on control samples is representative of that deposited on production hardware. Understanding the influence of the different substrate properties would enable more representative control samples to be designed and the effectiveness of the process control methods improved. A set of experiments were completed to compare the influence of two surface finishes (ground and grit-blasted) and two superalloys (cast single crystal CMSX-3 and annealed Inconel 718) on Laser Blown Powder structures. A single layer was deposited on small sample plates to investigate deposition geometry. In this study, laser power and travel speed are used to vary the heat input while powder feed rate is adjusted according to the travel speed to maintain a constant linear feed rate. This work highlights the role of key variables on the deposition geometry. It was found that the two materials show similar responses, even though they have different compositions and differing thermo-physical properties. In the range investigated the surface texture exhibits the greatest influence with large variation in deposit width and penetration. Surfaces whose appearance had been dulled through grit blasting absorb much more energy than ground surfaces due to a higher disposition for multiple scattering.