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Proceedings Paper

Laser surface annealing of Ni-base superalloy for enhancement of material performance in hydrogen environment
Author(s): Akio Hirose; Liufa Liu; Kojiro F. Kobayashi
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Paper Abstract

In the present work, laser surface annealing has been applied to an age-hardened Ni base supper alloy Inconel 718 using a 2.5kW CO2 laser to improve its performance in hydrogen environment. Laser surface annealing can produce a locally solutionized zone at the surface of Inconel 718. In the solutionized zone the age precipitates of (gamma) ' and (gamma) '' are dissolved in the matrix, and thereby the hardness of the solutionized zones is reduced to below 250Hv from approximately 450Hv of the aged base metal hardness. The surface softened zones having several hundred micro meters in depth can be obtained without melting the treated zone by controlling the laser parameters, i.e. thee defocus distance and traverse speed. Having much greater ductility than the aged base metal in hydrogen environment, the surface softened zones can effectively prevent hydrogen induced cracking, which tends to occur at the surface of a stress concentrated region. In the present case, the ductility of the surface annealed specimen is almost twice that of the base metal in a tensile test under a 29.3MPa hydrogen atmosphere at room temperature with hydrogen pre- charging. Since a controlled laser irradiation can precisely and locally anneal the surface of a stress concentrated region where hydrogen induced cracking is liable to occur, a sacrifice of strength of the structure caused by the surface softening is negligible.

Paper Details

Date Published: 6 November 2000
PDF: 4 pages
Proc. SPIE 4088, First International Symposium on Laser Precision Microfabrication, (6 November 2000); doi: 10.1117/12.405753
Show Author Affiliations
Akio Hirose, Osaka Univ. (Japan)
Liufa Liu, Osaka Univ. (Japan)
Kojiro F. Kobayashi, Osaka Univ. (Japan)

Published in SPIE Proceedings Vol. 4088:
First International Symposium on Laser Precision Microfabrication
Isamu Miyamoto; Koji Sugioka; Thomas W. Sigmon, Editor(s)

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