Effect of Welding Processes on Fatigue Behaviour of AISI 409M Grade Ferritic Stainless Steel Joints

The present investigation is aimed at to study the effect of four welding processes namely friction stir welding, gas tungsten arc welding, laser beam welding and electron beam welding on fatigue behavior of the ferritic stainless steel conforming to AISI 409M grade. Rolled plates of 4 mm thickness were used as the base material for preparing single pass butt welded joints. The fatigue life and fatigue crack growth behavior were evaluated using hourglass and centre cracked tension (CCT) specimens respectively. A 100 kN servo hydraulic controlled fatigue testing machine was used under constant amplitude uniaxial tensile load with stress ratio of 0.1 and frequency of 15 Hz. Fatigue properties are correlated with the tensile, impact toughness, micro hardness, microstructure, fracture surface morphology and residual stress of the welded joints. It is found that the joint fabricated by friction stir welding process showed superior fatigue life and fatigue crack growth resistance compared to other joints. This is mainly due to the synergetic effect of dual phase ferritic-martensitic microstructure, superior tensile properties and favorable residual stress, which inhibit the growth of cracks compared to other joints.