Evaluation of microstructure, mechanical properties and pitting corrosion in dissimilar of alternative low cost stainless steel grade 204Cu and 304 by GTA welding joint

Abstract

In this present work, solutions are sought regarding the problems of dissimilar welding of austenitic stainless steel for industrial fabrication work. There is support for the popular 200 grade stainless steel as a low-cost alternate to for 300 series grade in developing countries in Southeast Asia, especially Thailand, Vietnam, Myanmar, Laos and Cambodia. This study evaluates the microstructure, mechanical properties and pitting corrosion of dissimilar welding of the alternative low cost stainless steel grades 204Cu and 304 employing a GTA welding process by using different filler metals, namely 309L and 316L. It was found that for both weld metals and both filler metals the melting area in 204Cu BM side was larger than the 304 BM side. The delta-ferrite content in the weld metal of 309L was lower than 316L, HAZ and PMZ on the 204Cu side was wider than the 304 side of both welded metals. For the mechanical properties, the hardness volume of the welded metal of the 309L was higher than the 316L. Hardness adjacent to the fusion line of the 304 side was lower than the 204Cu side of both the filler metals. The tensile strength of the welded metal of 316L was more than the 309L and both welded metals ductile fractured in the welded zone (close to the 304 BM side). The pitting corrosion resistance of the welded metal for 309L was higher than for 316L and both welded metals initiated pitting at the boundary between the austenite phase and the delta-ferrite phase.