Mechanical and corrosion properties of TIG welded dissimilar AISI 420 and UNS S32205 stainless steel sheets

Duplex (ferritic-austenitic) stainless steels such as UNS S32205 are especially preferred for their resistance to corrosive environments such as sea water, while providing mechanical properties, which are comparable to those of structural steels. These steels include phases of delta-ferrite and austenite in approximately equal amounts. These alloys are used by traditional industries mainly in water refining systems, bridges, and chemical tanks. Martensitic stainless steels such as AISI 420 are chosen for applications where especially high mechanical properties are a major requirement as well as for their adequate resistance in corrosive media. For economic and technical considerations, these two different types of alloys can be used together in various applications. In this study, 3-mm-thick sheets of UNS S32205 and AISI 420 stainless steels were joined via tungsten inert gas (TIG) welding under pure argon shielding gas using ER312 and ER2209 filler metals. Microstructural examinations of the alloys as received, the weld metals, and the heat affected zones were achieved using both metallurgical and scanning electron microscopes. The composition of the filler material changed the microstructural, mechanical, and corrosion properties of the weld metals. The samples joined with the ER312 and ER2209 fillers yielded weld metal microhardness values of 272 HV and 258 HV, respectively, whereas the impact energy values of the samples were detected as 15 J and 34 J, respectively. The samples joined using ER2209 and ER312 fillers exhibited weld metal corrosion rates of 0.1523 and 0.1331 mm.year(-1).