Feasibility study on dissimilar joining of ferritic/martensitic and austenitic steels using handheld laser beam welding

Handheld fiber laser-beam welding (LBW) is relatively a new technology that mainly uses laser-beam as energy source to achieve welding purpose. IN-RAFMS and SS316L plates of 6 mm thickness were used to obtain their both similar and dissimilar trial joints on handheld fiber LBW machine with 2 kW maximum-power; 5000 Hz maximum-frequency; and 99.99% pure argon shielding gas. Bead-on-plate (BOP) trials were performed individually on IN-RAFMS and SS316L plates of same thickness to arrive at best combination of handheld fiber LBW parameters in terms of welding speed and laser power for achieving sound welded joints. Post-weld-heat-treatment (PWHT) at 750 °C/2 h followed by furnace cooling was done on similar IN-RAFMS to IN-RAFMS and dissimilar IN-RAFMS to SS316L joints. Basic characterization included; radiographic testing (RT), stereo-microscopy, optical-microscopy, and post-weld Vicker’s microhardness (250 g/10s). Summarily, obtained results did not yield expected sound welds; because of porosity, solidification cracks, and δ-ferrite in fusion zone. These limitations were primarily attributed to low laser power and manual control of welding speed. Consequently, this feasibility based investigation highlights challenges associated with handheld fiber LBW and concludes need for improved power, parameter optimization, automation of welding speed, and trailing gas with diffuser for sound dissimilar LBW joints of studied steels.