CVN impact energy and fracture characteristics correlations with different oxide nanoparticles improving submerged arc welds

The main aim of this research is to correlate the toughness improvement with fracture features of tested Charpy V-Notch impact specimens obtained from submerged arc welds enriched by different oxide nanoparticles (TiO2, SiO2, Al2O3 and Mn2O3). Through Scanning Electron Microscopy (SEM) fractography, fracture features were determined, which are the shear fracture percent, the loading angle, as well as the diameter of dimples and the width of cleavage sheets at ductile and brittle fracture regions, respectively. It was observed an increase of the Charpy V-Notch impact energy with the decrease of loading angle and the average diameter of dimples, as well as with the increase of its shear fractures percents. Moreover, it was correlated the increase of Acicular Ferrite surface density with the decrease of width of cleavage sheets. Thus, the toughness of the submerged arc welds can be improved by adding TiO2, SiO2, Al2O3 or Mn2O3 nanoparticles.