Microstructural, Mechanical Properties and Corrosion Resistance of Ferritic Stainless Steel Welded by GTAW and Coated by Flame Spraying

Abstract

Ferritic stainless steels are widely used in transportation industry due to their exceptional performance regarding mechanical and corrosion properties. However, after a welding process, joints feature the sensitizing phenomenon because of the heat exchange from the torch affecting mechanical properties and corrosion resistance. This work describes the behavior firstly of mechanical properties of weld joints of ferritic stainless steel as base material without and with filler material (AISI 308L) by gas tungsten arc welding (GTAW). Operating parameters such as arc voltage, welding currrent, welding speed, feed speed, shielding gas flow were evaluated. Secondly, samples of weld joints were coated by flame spraying of composite particles in order to reduce the weight loss induced by corrosion in a salt spray (fog) apparatus. Changes induced from GTAW on the heat affected zone and Thermal Spraying on corrosion resistance, were monitored by optical and scanning electron microscopy, microhardness and longitudinal tensile testing. Results show that GTAW helps to control the size and the microstructure of heat affected zone improving simultaneously the mechanical properties. Meanwhile, welded joints covered by composite coatings feature a lower damage provided that the ceramic phase has been homogeneously dispersed.