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Proceedings Paper

Laser surface melting of martensitic stainless steel 440C for enhancing corrosion resistance
Author(s): Chi-Tat Kwok; Ka-Hing Lo; Fai-Tsun Cheng; Hau-Chung Man
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Paper Abstract

Surface modification of martensitic stainless steel 440C was achieved by laser surface melting using a 2-kW continuous wave Nd:YAG laser. The corrosion characteristics of laser-melted specimens fabricated under different processing parameters in 3.5% NaCl solution at 23°C were studied by potentiodynamic polarization technique. The pitting corrosion resistance of all laser-melted specimens was significantly improved, as evidenced by a shift of the pitting potential in the noble direction, a wider passive range, and a lower passive current density. The pitting potential of the laser-melted specimen fabricated under a power density of 4.2 kW/cm2 and a scanning speed of 25 mm/s (specimen P12-440C-25) was increased to 200 mV (SCE), which was much higher than that of annealed and conventionally heat-treated 440C. The pitting corrosion characteristics of the laser-melted specimens were strongly dependent on the processing conditions which resulted in different microstructures. The enhanced pitting resistance resulted from the combined effect of dissolution or refinement of carbide particles and the presence of retained austenite. By using different processing parameters, it was found that the pitting resistance of the laser-melted specimen P12-440C-25 was the highest by virtue of a high volume fraction of retained austenite and a small amount of precipitated carbide.

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: 10.1117/12.497599
Show Author Affiliations
Chi-Tat Kwok, Univ. of Macau (Macao)
Ka-Hing Lo, Hong Kong Polytechnic Univ. (China)
Fai-Tsun Cheng, Hong Kong Polytechnic Univ. (China)
Hau-Chung Man, Hong Kong Polytechnic Univ. (China)

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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