Substrate influence in laser blown powder of nickel superalloys

摘要

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