Characterization of laser welds in Al–10wt.%Si coated ferritic stainless steel

• Published in: Materials in engineering Vol. 32; no. 2; pp. 917 - 925
• Main Authors: Kong, Jong Pan, Park, Tae Jun, Kim, Jeong Kil, Uhm, Sang Ho, Woo, In Su, Lee, Jong Sub, Park, Bong Gyu, Kang, Chung Yun
• Format: Journal Article
• Language: English
• Published: 01.02.2011
• Subjects: Aluminum; Base metal; Boundaries; Ferritic stainless steels; Hardness; Heat affected zone; Laser beam welding; Microstructure; Welded joints
• ISSN: 0261-3069
• DOI: 10.1016/j.matdes.2010.08.026

409L stainless steel hot-dipped with Al-10wt.%Si was welded using CO2 laser and the microstructure and hardness of the weld were investigated. When the specimen was welded with laser power of 5kW and welding speed of 5m/min, full-penetrated sound weld was obtained. With that specimen, the relationship between the microstructure and hardness of the weld was examined. The hardness of the weld was the highest in the fusion zone (FZ) and decreased to the base metal (BM) via heat affected zone (HAZ). The hardness of the HAZ near bond line was also higher than that near the base metal. The maximum hardness in the fusion zone could be explained by the existence of the precipitates, that is, TiN, Ti(C,N), Al2O3 and Al2O3 +TiN mixed compounds with the size of 500nm, and solution strengthening due to the elements Al and Si dissolved from the coating layer to the fusion zone. There were subgrains within the HAZ and more in the area near the bond line. In addition, fine TiC particles with the size under 50nm was precipitated in the sub-grain boundaries. The formation of sub-grain boundaries and the particles precipitated in the boundaries might contributed to the high hardness in the HAZ.