Product Code: PIC2008_609

Microstructure and Corrosion Behavior of Laser Welds Between Dissimilar Stainless Steels
Authors:
Chi Tat Kwok, University of Macau; Taipa Macau Peoples Republic of China
S.L. Fong, University of Macau; Taipa, Macau Peoples Republic of China
F.T. Cheng, The Hong Kong Polytechnic University; Hung Hom, Kowloon Hong Kong
H.C. Man, The Hong Kong Polytechnic University; Hung Hom, Kowloon Hong Kong
Presented at PICALO 2008

In recent years, laser beam welding becomes very popular in joining dissimilar materials for improving performance and reducing cost of the engineering components because of its accuracy, precision, repeatability and low distortion. In the present study, six autogenous dissimilar welds with the combinations of austenitic (S30400 and S31603) and duplex (S31803 and S32760) stainless steels were fabricated by laser welding using a 2.5 kW CW Nd:YAG laser in an argon atmosphere. The microstructure, phases present and compositions in the resolidified zone of the welds were analyzed by optical microscopy, X-ray diffractometry and energy dispersive spectroscopy (EDS), respectively. The microhardness of the welds was measured by means of a microhardness tester. The corrosion behavior of the dissimilar welds in 3.5% NaCl solution at 23 oC was studied by means of cyclic potentiodynamic polarization. X-ray diffraction and EDS analysis showed that the phases present in the welds depended on the mixing of compositions and the combinations of the parent steels (austenitic-austenitic, austenitic-duplex and duplex-duplex). While the welds between austenitic-austenitic and duplex-duplex steels retained the original austenitic and duplex structures respectively, the austenitic-duplex welds contained austenite as the major phase and -ferrite as the minor phase. The hardness of the dissimilar welds was comparable to that of the similar welds. All dissimilar welds exhibited passivity. The pitting corrosion resistance of the welds between S31603-S32760 and S30400-S32760 are comparable to the unwelded S32760 as evidenced by a high pitting potential.