Optimization of Ni content in the deposited weld metal composition of E7018-G electrode

In the present study, effect of Ni alloying element on the characteristics of deposited weld metal of E7018-G electrode was evaluated. Therefore, electrodes contained different amounts of Ni (0-1.7wt.%) were designed, manufactured and welded via SMAW process. Microstructural studies revealed dichotomy effect of Ni on the deposited weld metal microstructure, i.e. increasing the Ni content up to 1.2wt.% improved the formation of acicular ferrite in the weld metal microstructure and caused significant grain refinement at the reheated zone of weld metal. While, higher Ni content (>1.2wt.%) resulted in some raising in the widmannstatten ferrite content in the weld metal. Strength multiplied by impact energy parameter (UTS×CVN) was used for mechanical properties assessment. Mechanical properties evaluation revealed the highest UTS×CVN parameter achieved in the weld metal contained 1.2wt.% Ni. Hardness of the weld metal increased with increasing Ni content which is related to the formation of micro constituents in the microstructure of weld metal and increasing their content with increasing Ni content.