Abstract
The present study is concerned with laser beam welding and its effect on size and microstructure of fusion zone then, on mechanical and corrosion properties of duplex stainless steel welded joints. In this regard, influence of different laser welding parameters was clarified. Both bead-on-plate and autogenously butt welded joints were made using carbon dioxide laser with a maximum output of 9 kW in the continuous wave mode. Welded joints were subjected to visual, dye penetrant and radiography tests before sectioning it for different destructive tests. Accelerated corrosion test was carried out based on tafel plot technique. The results achieved in this investigation disclosed that welding parameters play an important role in obtaining satisfactory properties of welded joint. High laser power and/or high welding speed together with adjusting laser focused spot at specimen surface have produced welded joints with a remarkable decrease in fusion zone size and an acceptable weld profile with higher weld depth/width ratio. Besides, acceptable mechanical and corrosion properties were obtained. Using nitrogen as a shielding gas has resulted in improving mechanical and corrosion properties of welded joints in comparison with argon shielding. This is related to maintaining proper ferrite/austenite balance in both weld metal and HAZ in case of nitrogen shielding. As a conclusion, laser power, welding speed, defocusing distance and type of shielding gas combination have to be optimized for obtaining welded joints with acceptable profile as well as mechanical and corrosion properties.
Highlights
The duplex stainless steels have been developed to provide a combination of strength and resistance to pitting and stress corrosion cracking in comparison with the 300-series austenitic stainless steels [1,2,3]
Based on the results achieved in this study, it can be concluded that laser power, welding speed, defocusing distance and type of shielding gas combinations have to be optimized for obtaining welded joints with acceptable fusion zone size, weld profile as well as mechanical and corrosion properties
The minimum fusion zone produced by laser beam is depended on heat input as a function of laser power and welding speed
Summary
The duplex stainless steels have been developed to provide a combination of strength and resistance to pitting and stress corrosion cracking in comparison with the 300-series austenitic stainless steels [1,2,3]. The optimum properties of duplex stainless steels are achieved when nearly equal proportions of austenite and ferrite are present in the microstructure. In base metals, this phase balance is obtained by an appropriate combination of composition and solution heat treatment. The present study is concerned with laser beam welding and its effect on size and microstructure of fusion zone on mechanical and corrosion properties of duplex stainless steel welded joints
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