EVOLUTION OF STRUCTURE, PHASE AND MECHANICAL PROPERTIES DUPLEX STAINLESS STEEL (DSS) 31803 WELDING USING GMAW WITH THE ADDITION OF CO2 TO Ar - CO2 SHIELDING GAS

The purpose of this study was to analyze the effect of CO2 on the composition of the Ar- CO2 shielding gas in DSS 31803 duplex welding using GMAW on carbon deposition, ferrite fraction, microstructure, weld and HAZ mechanical properties. This study uses A (100% Ar), M1 (95% Ar + 5% CO2), M2 (90% Ar + 10% CO2), M3 (85% Ar + 15% CO2), M4 (80% Ar + 20 % CO2), M5 (75% Ar + 25% CO2) and C (100% CO2). From the results of the study, the microstructure of the weld metal in each specimen contained grain boundary austenite (GBA), Widmanstätten austenite (WA), intragranular austenite (IGA), and partial transformed austenite (PTA). Scanning electron microscopy (SEM) identifies the occurrence of chrome carbide precipitation (Cr23C6) HAZ region in specimens M5 and specimen C. The equilibrium phase of ferrite and austenite in weld metal areas is fulfilled in specimens A (34.8), M1 (38.9), M2 (36.4), M3 (38.4) and M5 (45.9). The highest average hardness value of vikers in weld metal area is found in M5 specimen which is 255 HV. While the lowest value in specimen C is 238 HV.The highest Vickers average hardness value in the heat affected zone (HAZ) is in specimen A which is 271 HV and the lowest hardness is in specimen C which is 245 HV. High tensile strength values are found in specimen M5 with value 800 MPA. While the value of low tensile strength in M4 specimens which is 652 MPA