Introduction. Improving the efficiency of arc surfacing with a consumable electrode is one of the key vectors in the development of modern manufacturing. Split-arc gas-shielded welding with a consumable electrode is of particular interest. The electrode arrangement in this welding process affects the fusion zone, namely its shape and curvature. The shape of the penetration zone significantly affects the property gradient and the operational reliability of the coating. The effect of the electrode arrangement on the curvature of the penetration front remains quantitatively unassessed. The objective of this study is to quantitatively evaluate and determine the correlation of the curvature of the penetration shape depending on the relative arrangement of the electrodes.

Materials and Methods. The effect of electrode positioning on the penetration shape was studied by building up six layers and subsequently analyzing the fusion shape in the base metal. The selected influencing parameters were the interelectrode distance (z) and the electrode inclination angle (α). The surfacing process was performed in an Ar/CO₂ shielding gas atmosphere in a ratio of 98/2%. To make the fusion zone visible, the transverse cross-sections of the layers were subjected to etching. The fusion zone boundaries were digitized. A 6th-degree polynomial was used to determine the functions describing the penetration shape. The obtained functions were differentiated to analyze the fusion shape. The first-order derivative was used to determine the number of extremes. To assess the curvature of the penetration shape, the average value of the absolute second derivative was calculated over the range of values within the layer width. Correlation was established using Pearson's method.

Results. As a result of the conducted experiment, a quantitative assessment of the curvature of the penetration shape depending on the relative arrangement of the electrodes was performed. Functions describing the penetration shapes were determined. The curvature of the obtained shapes and the number of extremes were calculated. Correlation coefficients between the interelectrode distance, the electrode inclination angle, the penetration curvature, and the number of extremes were determined. It was found that the curvature of the penetration shape and the number of extremes weakly depend on the interelectrode distance. The electrode inclination angle determines the penetration curvature to a greater extent. A damping effect of the heat flux of the electric arc by the volume of the weld pool was identified at an interelectrode distance of 15 mm.

Discussion. In each experiment, the base metal fusion zone displayed a saddle-shaped geometry. Increasing the electrode included angle resulted in a shallower penetration shape, attributed to an alteration in the vector of electromagnetic forces that govern plasma streams and molten metal droplet transfer. The damping effect occurred because reducing the interelectrode distance enlarged the weld pool. A layer of molten metal, possessing high heat capacity but low thermal conductivity, separated the electric arc from the base metal, thus damping the heat flux from the arc.

Conclusion. The conducted study made it possible to quantitatively assess the effect of the electrode arrangement on the curvature of the penetration shape, as well as to determine the degree of influence of the interelectrode distance and the electrode inclination angle on the curvature of the penetration shape. The interelectrode distance was found to have a weak effect on both the fusion shape curvature and the number of extremes. The correlation coefficients for these parameters  were –0.22 and 0.43. The effect of the electrode inclination angle on both the fusion shape curvature and the number of extremes was considered substantial. The correlation coefficients for these parameters were –0.65 and –0.71. As the angle of inclination of the electrodes relative to the vertical increased, the curvature of the penetration shape decreased.