Evaluation of Microstructure and Mechanical Properties of Dissimilar Welded Joint between 32750 Super Duplex Stainless Steel and 304L Austenitic Stainless Steel

In this study، the microstructure and mechanical properties of dissimilar welding of Super duplex stainless steel UNS 32750 to austenitic stainless steel AISI 304L by gas tungsten arc welding process with direct current electrode negative polarity was investigated. For this purpose، two filler metals including ER25104L and ER309LMo were used. The microstructure of the different zone in each joint، including weld metals، heat affected zone، interface were evaluated using optical microscopy and the relationship between mechanical properties and microstructure of welded joints is evaluated. Results indicate that austenitic and ferritic structures such as dendrite in the weld metal 25104L، 309LMo weld metal was observed as the primary ferrite with austenitic matrix. In addition microstructure was seen as skeleton ferrite morphology. In addition، the mechanical properties including the bend test، ultimate strength، impact resistance and hardness were investigated. All the specimen underwent ductile fracture in HAZ in the tension test. The maximum fracture energy related to ER25104L. The welded specimen with ER25104L filler metal showed the maximum elongation. The maximum and minimum hardness corresponded to the ER25104L and ER309LMo، respectively. Mechanical properties of joints welded by the two kinds of filler metals are satisfactory، althought the mechanical properties of 25104L filler metal is superior to that by 309LMo filler metal. Based on the present work، it is concluded that 25104L provides the optimum qualities for joining dissimilar metals between 32750 super duplex stainless steel and 304L austenitic stainless steel