Relationship Between Corrosion Resistance and Microstructure Characteristic of Single-Pass Laser-Arc Hybrid Welded Stain
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INTRODUCTION
STAINLESS clad steel plate (SCSP) is a composite structural material made by bonding stainless steel (cladding layer) and carbon steel (base layer). It has been an economical alternative to stainless steel, and widely applied in high-energy defense, food processing, and medical fields.[1,2] However, the corrosion resistance of SCSP weld can easily deteriorate because of the mixture of cladding layer and base layer during welding.[2,3] In multi-pass arc welding of 16MnR/AF2205 SCSP, Wang et al.[4] found the weld corrosion resistance was weakened because of the formation of a carbon-rich layer between carbon steel and fusion zone. Chen et al.[5] also found that the susceptibility of stress corrosion cracking (SCC) of arc welded low-alloy steel/304L stainless steel SCSP was increased. Missori et al.[2] employed Cr-rich and Ni-rich strips in advance to avoid the dilution of base layer to cladding layer during single-pass laser welding of SCSP. Although the weld presented excellent mechanical properties due to free of defects, they did not consider the variation of weld corrosion resistance. The existing literature showed that acceptable corrosion resistance of SCSP weld could only be obtained by multi-pass welding with complicated
YUNFEI MENG, KAI KANG, MING GAO, and XIAOYAN ZENG are with the Wuhan National Laboratory for Optoelectronics (WNLO), Huazhong University of Science and Technology, Wuhan 430074, P.R. China. Contact e-mail: [email protected] Manuscript submitted September 4, 2018.
METALLURGICAL AND MATERIALS TRANSACTIONS A
processes and low efficiency, but is hard to be achieved by single-pass welding due to the severe mixture between base layer and cladding layer. Therefore, it is essential to develop a new method with high efficiency for the joining of SCSP to obtain excellent corrosion resistance, and promote its industrial application. Laser-arc hybrid welding shows great potential for the welding of SCSP because it combines the advantages of both laser welding with high power density, and arc welding with high filling efficiency. On the one hand, the welding efficiency and the weld mechanical properties can be improved by laser-arc synergic effects.[6,7] On the other hand, the weld corrosion resistance can be also strengthened by laser-arc hybrid welding with only one pass.[3,8,9] Chen et al.[10] improved the pitting corrosion resistance of laser-arc hybrid welded austenitic stainless steel by applying an external magnetic field. Kelsey et al.[11] found that increasing heat input increased the SCC susceptibility of laser-arc hybrid welded SCSP. It is worth mentioning that we had obtained a SCSP weld with nearly equal corrosion resistance to base metal (BM) by single-pass laser-arc hybrid welding under a large laser-arc distance (DLA) of 9 mm, where the charge transfer resistance (Rct) increased to 89 pct of the BM, and the corrosion current density (Icorr) decreased by ten times to close to the BM.[3] However, many publications[12–16] had proved that the optimal DLA for hybrid welding was 2 to
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