Additive and subtractive laser-pulsed nano/micro machining of metal alloys for enhanced material properties, and numerical validation
Bashir, Mahmood Al
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This research focuses on two different aspects of laser machining process, namely additive and subtractive laser micromachining, for inherent improvements to metallic surfaces. In both the processes, material surfaces are enhanced to attain specific properties based on the application of the material. An AVIA 355® nano-second laser and a Coherent® Diamond J-3 series microsecond CO2 laser was used to create sintered structured using Cu particles. The textured surfaces were examined under SEM, MicroXAM™ 100 profilometer and Keyence® VK-X100 were used to distinguish the surface structures and study its material properties. Moreover, the melt depth of the textured surface was compared with diffusion length equation to validate the findings. A comparison of nanosecond and microsecond pulsed laser surface structure was also performed to understand the difference and similarities between them. An FVM (Finite Volume Method) TruFlow™ model was developed in Flow 3D™ to analyze and compare the thermally induced surface microstructural changes with the experimentally observed results. The experimental, analytical and numerical analyses show very good agreement with each other and validates the hypothesis. The initial sintering results show the successful fabrication of a sintered single layer metallic powder structure with controlled porosity, using pulse period of 1000μs, pulse width of 205 μs with a defocused beam. The laser-sintered structure is compared with that of the conventionally sintered sample, which shows similar manufacturing quality. The particles were also pressed in a hot press prior to sintering to ascertain its effects. The main benefit of this new manufacturing process also includes a significant reduction in manufacturing time. The obtained results provide a crucial step towards developing a new class of manufacturing process for the metallic porous structures.
Thesis (Ph.D.)-- Wichita State University, College of Engineering, Department of Mechanical Engineering