Study & Evaluation of Suitable Shielding Gas Mixture for Super Duplex SS Weld Overlay by Gas Metal Arc Welding Process

Development of new chemical products and processes, demand for materials with improved mechanical properties, metallurgical stability and greater corrosion resistance in aggressive environments. In present years number of new highly corrosion resistance alloys containing Nickel, Chromium and Molybdenum have been introduced to combat corrosion in aggressive environment in chemical, Pollution control, marine, oil and gas industries. Duplex and superduplex stainless steels are alternative to austenitic grades due to their higher strength and good corrosion resistance performance. In the present scenario there is a severe competition in the fabrication industry all over the world. As such economic factors as a rule will not permit fabricating components from solid high alloyed material. Hence cladding/weld overlay is widely practiced to reduce material cost. Objective of work was the evaluation of suitable shielding gas mixture for super duplex stainless steel weld overlay by GMAW process. Evaluation will carried out by taking trials with different gas/gas mixtures like Ar, Ar+1%O2, Ar+30%He+1%O2, Ar+15%He+2.5%N2, Ar+1%N2 & studying the effect of same on arc characteristic, weld bead appearance, ferrite measurement, metallography, chemical analysis, PRE number & corrosion resistance properties of weld overlay. Corrosion resistance properties will be studied by the pitting and crevice corrosion test.