Investigation of mechanical properties and microstructure characterisation of MMA-MIG-TIG-SAW welded EN8 steel joints via shot blasting method

Abstract

The industries of energy, transportation, and other engineering components all benefit greatly from the use of medium carbon (C) steel EN8. For these applications, welding is typically used to join the material. Conventionally welded joints, however, struggle to meet the exacting standards of industrial applications. In this comprehensive study, the tensile strength, microhardness, and microstructure of joints made of medium C EN8 steel using manual metal arc (MMA), metal inert gas (MIG), tungsten inert gas (TIG), and submerged arc (SAW) welding were investigated. These weld joints were then subjected to the shot blasting method to determine the effect on the mechanical properties of these weldments, Different response characteristics have been studied in relation to the shot blasting with various time periods. A detailed characterisation of the samples has been carried out optical microscopy, surface electron microscopy (SEM), energy dispersive spectroscopy (EDS), optical emission spectroscopy (OES), microhardness, and tensile testing with fractographical analysis. The maximum percentage increase in the microhardness in fusion zone (FZ) occurred in case of TIG welded specimens, i.e. 29.63% after 25 min of abrasive blasting period. However, the maximum change in the tensile strength, i.e. 10.53% has been observed for MMA welded specimens after 15 min of abrasive blasting period. Microstructural analysis revealed TIG has a columnar dendritic structure, MIG and SAW have an equiaxed dendritic structure. MMA has a cellular dendritic structure. The outcomes revealed that abrasive blasting improves the mechanical characteristics of industrial MMA, MIG, TIG, and SAW welded specimens.