Investigation of mechanical properties and corrosion behavior of inconel 625 and aisi 316 l materials combined with tig welding method

In this thesis it was studied on dissimilar metal welding of nickel based super alloy Inconel 625 and austenitic stainless steel AISI 316L which are commonly used in nuclear, chemical and petrochemical industries. Two types of TIG (Tungsten Inert Gas) welding processes as continuous and pulsed current were used. Three filler types used for each welding processes as; ERNiCr-3, TIG 316L and twisted (ERNiCr-3 + TIG 316L). Totally 6 experimental setups were investigated as macro structural, micro structural, mechanical and corrosion behavioural properties. As a result of study it is detected that using pulsed current type instead of continuous type TIG is reduce formation of harmful secondary phases. It is known that Inconel 625 and ERNiCr-3 filler metal consist Nb element which cause formation of Nb based secondary phases. Therefore, TIG 316L selected as Nb free filler metal. But despite this it was determined Nb based secondary phases at the weld zone. It was convinced that excess heat input because of multipass welding process for thick plates caused this case. After the welding process several elements detected at the SEM/EDAX analsys of some experiments which are not in chemical compositions of base and filler metals. Welding equipments are must be cleaned before welding and welding process should be carry out inside an insulated area. According to the all micro structural, mechanical and corrosion tests, twisted filler metal showed the best results.