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Proceedings Paper

Laser surface annealing technique of aged Inconel 718 by laser-beam irradiation
Author(s): Liufa Liu; Akio Hirose; Kojiro F. Kobayashi
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Paper Abstract

Laser was employed to anneal a thin surface layer of aged Inconel 718 by dissolving the strengthening phase, γ". The HE (Hydrogen Embrittlement) resistance of the alloy was improved via such laser surface annealing (LSA) processes. To establish a general LSA technique for engineer applications, experimental LSA processes were conducted to study the effects of the laser process parameters on the formation of the annealed surface layers, and applicable process parameter ranges were obtained. Next, a numerical method was developed for predicting the formation of the laser annealed surface layers in the following steps. Because only the γ" phase was dissolved in the LSA process, the dissolution kinetics of this phase was studied via thermal cycling experiments, and it was proved to follow an Avrami equation. FEM (Finite Element Method) simulations were conducted to calculate the thermal distribution in each laser annealed surface layer, and thermal history data were extracted every certain depth. The volume fractions of the γ" phase at these depths were calculated using these thermal history data based on the deduced Avrami equation. Using a developed relationship between the hardness variation of the alloy and the volume fraction variation of the γ" phase, the hardness distribution in the annealed surface layer and this layer's thickness were calculated. The predicted applicable laser process parameter ranges were obtained. These calculated results were compared with their corresponding experimental results. The good agreements between the calculated and measured results suggested that this numerical prediction approach is feasible for engineer applications.

Paper Details

Date Published: 3 March 2003
PDF: 6 pages
Proc. SPIE 4831, First International Symposium on High-Power Laser Macroprocessing, (3 March 2003); doi: 10.1117/12.497895
Show Author Affiliations
Liufa Liu, Osaka Univ. (Japan)
Akio Hirose, Osaka Univ. (Japan)
Kojiro F. Kobayashi, Osaka Univ. (Japan)

Published in SPIE Proceedings Vol. 4831:
First International Symposium on High-Power Laser Macroprocessing
Isamu Miyamoto; Kojiro F. Kobayashi; Koji Sugioka; Reinhart Poprawe; Henry Helvajian, Editor(s)

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