Mechanical and corrosion behaviour of conventional and high-speed remote scanner laser welding for duplex stainless steel: A comparative study

Abstract

High-speed remote scanner laser-welding is a relatively new technique that is being tried out at the Mittweida Laser institute to weld stainless steel sheets of high thicknesses; the material used was (1.4462) 8mm thick. For comparison, the material was welded also by gas tungsten arc welding (GTAW) or TIG. The welding processes were evaluated by several testing techniques; mechanical testing using (tensile testing and hardness). Optical microscopy was employed to investigate the phase changes and weld defects inside the material. Scanning electron Microscope investigated the grain size before and after weld with the precipitate. Electrochemical corrosion testing was used to evaluate the corrosion behaviour of the weld zone. For each experiment, base metal and heat affected zone (HAZ) have been selected. Microstructure investigation of HAZ revealed the formation of finer microstructures with different grain boundaries due to the melting and the resolidification of the base metal and extensive microstructure changes inside the materials. In comparison to TIG, many weld defects were observed and carbide precipitations formed at the grain boundaries. Hardness measurements revealed that hardness increases towards the centre of both laser and TIG. Tensile testing revealed that the weld has the potential to have very high strength approaching that of the original material, particularly for laser welding. Measuring corrosion rates shows that the welded material is more susceptible to corrosion and to pitting, the pitting potential was estimated reflecting higher pitting resistance for base metal than laser and TIG weld respectively, thus can be explained due to the formation of precipitates of carbide and ferrite particularly for TIG Weldament.