Nickel-chromium-molybdenum alloys are especially used in manufacturing components for the aeronautical and the petrochemical industries. This article focused on determining the microstructural performance of this kind of alloy, welded with E NiCrFe-3 of 3,25 mm diameter electrode. The butt welding was obtained by preparing the edges at 60°. The microstructural variations were evaluated by optical microscopy, and the hardness analysis was carried out in the affected areas by the thermal welding cycle. To determine chromium and nickel equivalent, the Schaeffler diagram was used, which allowed obtaining the chemical composition resulting from the deposit. The structure of this alloy in the joint is austenitic, and it was determined by structural transformations consisting of skeleton type ferrite morphology, aligned the heating source of the electric arc. It was also proved the formation phases of primary austenite, austenite Widmanstátten, and the precipitation of secondary austenite to the interior of the ferrite, where structure of austenite Widmanstátten is the most fragile.