The present paper aims to compare the microstructural and mechanical properties of CK45 carbon steel plates, joined by friction stir (FSW) and tungsten inert gas (TIG) welding methods. Besides visual inspection, the welded joints and the base material were subsequently evaluated in respect of optical microstructures, hardness and tensile properties. Sound joints could be accomplished using both the FSW and TIG welding methods through proper selection of process parameters and the filler metal. The influence of a water-cooling system on the FSW and various filler metals on the quality of TIG welding were further assessed. Both the FS welded sample as well as TIG welded samples with two different filler metals ER70S-6 and ER80S-B2 exhibited brittle behavior that could be mitigated through optimized water cooling and use of R60 filler metal. A drastic reduction of brittle martensite phase constituent in the microstructure corroborated significant improvements in mechanical properties of the welded zones for both the FSW sample as well as TIG welded samples with R60 filler metal.
Keywords: carbon steel; friction stir welding (FSW); macrostructure; mechanical properties; microstructure; tungsten inert gas (TIG) welding.