Sensitization is one of the corrosion mechanisms which cause widespread problems in stainless steels, particularly in welded assemblies and improperly heat-treated work pieces heated at 500 to 800°C. As the Cr-rich carbides and sigma phase form, they deplete their neighboring regions of Cr, thereby lowering the Cr contents of the surface oxides over these regions. Once the contents of Cr in the regions adjacent to the carbides drop below 12 wt%, the oxide layers lose their protectiveness. Then the stainless steels will suffer from intergranular corrosion attack. Laser surface melting (LSM) can be easily achieved by melting the surface with a laser beam followed by rapid solidification for homogenizing chemical compositions, desensitization of improperly heated surface (i.e. redisolving the chromium carbides) and even removing surface cracks. In the present study, LSM of austenitic stainless steels (AISI 304, 321 and 347) and duplex stainless steel (AISI 2205) was attempted for desensitization by a 2.5 kW Nd:YAG laser and the susceptibility of the sensitized stainless steels before and after LSM to intergranular corrosion was also evaluated. The degree of sensitisation (DOS) of the stainless steels was determined by the double loop electrochemical potentio-kinetic reactivation method in solution of 0.5 M H2SO4 and 0.01 M KSCN at 25 °C by a potentiostat. The corrosion morphology and surface hardness were also investigated as well. Desensitization of stainless steels was successfully achieved by LSM and their intergranular corrosion resistance was found to be significantly enhanced as reflected by the decrease in DOS due to the low chromium depletion or possible solute segregation at the boundaries.
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4th Pacific International Conference on Laser Materials Processing, Micro, Nano and Ultrafast Fabrication
March 23–25, 2010
Wuhan, People's Republic of China
ISBN:
978-0-912035-56-7
PROCEEDINGS PAPER
Desensitization of austenitic and duplex stainless steels by laser surface melting
Weng Kin Chan;
Weng Kin Chan
1
Department of Electromechanical Engineering, University of Macau
, Taipa, Macau, China
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Chi Tat Kwok;
Chi Tat Kwok
1
Department of Electromechanical Engineering, University of Macau
, Taipa, Macau, China
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Kin Ho Lo;
Kin Ho Lo
1
Department of Electromechanical Engineering, University of Macau
, Taipa, Macau, China
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Zhichao Cheng
Zhichao Cheng
1
Department of Electromechanical Engineering, University of Macau
, Taipa, Macau, China
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Published Online:
March 01 2010
Citation
Weng Kin Chan, Chi Tat Kwok, Kin Ho Lo, Zhichao Cheng; March 23–25, 2010. "Desensitization of austenitic and duplex stainless steels by laser surface melting." Proceedings of the 4th Pacific International Conference on Laser Materials Processing, Micro, Nano and Ultrafast Fabrication. PICALO 2010: 4th Pacific International Conference on Laser Materials Processing, Micro, Nano and Ultrafast Fabrication. Wuhan, People's Republic of China. (pp. 806). ASME. https://doi.org/10.2351/1.5057219
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