A STUDY ON MECHANICAL AND METALLURGICAL BEHAVIOUR OF GMAW OF FERRITIC STAINLESS STEEL

Abstract

In this DISSERTATION an attempt has been made to develop a sound lap-fillet joint of ferritic stainless steel by optimizing the process parameters of GAS METAL ARC WELDING (GMAW), further weld metal was modified using Al and TiB2 with the help of pre-placement technique followed by GMAW. The weld joints were developed by using varying ratio and amount of powders of Al and TiB2 to get the refined grain structure so as to enhance hardness, tensile and fatigue properties. Scanning Electron Microscopy (SEM), X-Ray diffraction (XRD) and elemental dispersive analysis of X (EDAX) analysis of conventional welds and welds with powder addition were done to study its metallurgical behaviour. Tensile shear strength of conventional (unmodified) double and single lap-fillet weld was found to be more than that of the base metal. Fatigue life of conventional single lap-fillet weld increased significantly by decreasing the applied load. Microhardness test of conventional lap-fillet joint led to an observation of average hardness value of HAZ being more than that of base metal and very low value of hardness was observed at fusion boundary. Macro and microstructural analysis (using SEM) and hardness test of welded samples were conducted and it was found that modified welded joint corresponding to powder addition of Al and TiB2 in 1:2 led to higher hardness and finer equiaxed grains as compared to conventional welds (unalloyed).