Effect of ZrO2 nanoparticles on the impact properties of shielded metal arc welds

In the present study, the effect of ZrO2 nanoparticles in the electrode coating on the impact properties of shielded metal arc welds was investigated. The microstructure, Charpy impact properties and fracture surface morphology of welds were evaluated and the results were compared. When the ZrO2 nanoparticle content in the electrode coating was increased, the morphology of ferrite was changed from grain boundary ferrite to acicular ferrite and the impact toughness of welds were improved. The test results showed that the impact properties of welds could be well correlated with the volume fraction of acicular ferrite, number of ZrO2 inclusions and percentage of shear fracture area. •ZrO2 nanoparticles produced a uniform dispersion of ZrO2 inclusions in the weld.•The acicular ferrite microstructure nucleated at the ZrO2 inclusions.•Fine acicular ferrite improved the impact properties of weld.