Pitting corrosion resistance with shielded metal arc welding and post weld heat treatment on duplex stainless steel weld overlay
Duplex stainless steels (DSSs) are widely used in the marine environment, petro-chemical refineries, oil and gas industries because of their high corrosion resistance properties and balanced ratio of austenite and delta-ferrite phases. The objectives of this research are to an...
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| 格式: | Thesis |
| 语言: | English |
| 出版: |
2019
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| 主题: | |
| 在线阅读: | http://psasir.upm.edu.my/id/eprint/84367/1/FK%202019%20119%20-%20ir.pdf |
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| 总结: | Duplex stainless steels (DSSs) are widely used in the marine environment, petro-chemical
refineries, oil and gas industries because of their high corrosion resistance properties and
balanced ratio of austenite and delta-ferrite phases. The objectives of this research are to
analyze and evaluate the behavior of pitting corrosion, micro-hardness, microstructure and
chemical dilution effects of duplex stainless steel E2209 weld overlay with the hydrogen relief
(350°C), stress relief (650°C) and solid solution annealing (1050°C) heat treatments.
Shield Metal Arc Welding (SMAW) process with medium heat input produced a reasonable partitioning
ratio. The dilution has slightly increased in hydrogen heat treatment and a small reduction
for Stress relief heat treatment. Solution annealing with water quenching at above
critical point of A3 cooling temperature has shown the disappearance of heat affected zone
for low alloy steel substrate. Micro-hardness has indicated a substantial fluctuation of
hardness values in fusion zone. The solution annealing has shown a consistent
low hardness values at the weld overlay and hardened base metal region with the present of a large
amount of maternsite and noticed of equaxied ferrite structures. Ferrite count determination
in region of weld metal overlay are increased at hydrogen relief temperatures and
decreased at stress relief temperatures due to slow cooling which is more
favorable to austenite formation. The amount of ferrite in the weld metals has significantly
reduced with the solid solution anneal temperature due to sufficient time for the
formation of austenite and giving optimum equilibrium fraction in the welds. The major of
alloying elements which can contribute to intermetallic phases are analyzed. C, Cr and
Ni chemical elements have shown fluctuation values during PWHT. Whereas, N2 has produced
consistent values to prevent critical implication to nitride precipitation. The corrosion
weight loss has gradually increased with the increment of PWHT temperatures. At
solid solution annealing temperature, the weld metals are being restored with no significant of
weight loss. |
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