Measurement and Numerical Simulation of High Temperature Laser Material Processing.

High Temperature Laser Material Processing;Pulsed Laser Deposition;Laser Drilling;Direct Metal Deposition;Plasma Diagnostics;Mechanical Engineering;Engineering;Mechanical Engineering

Shin, JoonghanSastry, Ann Marie ;

University of Michigan

关键词: High Temperature Laser Material Processing;    Pulsed Laser Deposition;    Laser Drilling;    Direct Metal Deposition;    Plasma Diagnostics;    Mechanical Engineering;    Engineering;    Mechanical Engineering;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/78829/joonghs_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

This research investigates high temperature laser material processing, focusing on the applications for the aerospace industry. This study looks at three representative processes with three different interactions of plasma: 1) pulsed laser deposition (PLD) process for thin coating deposition where material deposit occurs via plasma and vapor, 2) drilling process for material removal to create shaped holes for efficient cooling and 3) direct metal deposition (DMD) process (very weak plasma) to clad a thick layer. In this study, thin coatings for two important turbine blade materials were produced by the PLD technique. Yttria-stabilized zirconia films produced by the PLD were very smooth and dense. The target stoichiometry was well preserved in films. The PLD technique was also used to deposit single crystal (SC) Ni-base superalloys on the substrates of the same material. The homoepitaxial growth of the SC Ni-base superalloy film was successfully obtained without re-melting of the substrate by the PLD process. Laser drilling experiments were carried out to generate cooling holes in an aerospace material, Inconel 718. The effect of the process parameters and different drilling methods on the hole qualities were comprehensively investigated. Using both the helical drilling technique at a high duty ratio (10 %) and O2 assist gas produces the best drilling performance under the acceptable drilling time (~5 s) for the industrial application. In this study, a numerical simulation for pulsed laser drilling was also carried out to provide the fundamental understanding of the high power density laser process and to investigate the effect of pulse format on the drilling performance. It was found that a modulated beam using a short pulse width and a high beam intensity yielded better drilling performance than the conventional pulsed laser under the same average power. Spectroscopic studies during laser drilling and DMD were carried out for the purpose of process diagnostics by employing the optical emission spectroscopy. The results indicate that plasma parameters can be used to monitor the drilling depth during laser drilling and the elemental composition created during the DMD.