Experimental study on the effect of austenitic stainless steel filler wires (AISI 308L & AISI 304L) on the metallurgical and mechanical properties of ferritic stainless steel AISI 409 welds

This study examines practical measures to mitigate crack formation in ferritic stainless-steel grade AISI 409 during Tungsten Inert Gas (TIG) welding. AISI 409 is widely used for mufflers and exhaust components. However, AISI 409 joints often developed fusion-line cracks following autogenous welding and the subsequent spinning process, resulting in over 20% rejection. To better understand how these failures occur, we examined the welding procedure, process parameters, and metallurgical aspects that may contribute to crack formation. As a corrective measure, AISI 409 plates were welded using AISI 308L and AISI 304L filler wires and then evaluated using Non-Destructive Testing, Metallography, Tensile Testing, and Fractography. The samples welded with AISI 308L showed a clear improvement in ductility, with elongation increasing by about 15%. This may be linked to its austenitic composition, which likely promotes a softer, more deformable weld metal. Fractography supported this observation, as the 308L joints exhibited a higher density of micro-voids, suggesting greater plastic deformation before fracture. Welds made with AISI 304L performed moderately better than the autogenous welds but did not match the improvements seen with 308L. Overall, the results point to a systematic route for improving weld integrity and significantly lowering rejection rates in AISI 409 components used in the automotive sector, which in turn supports better consistency and reliability in industrial applications.