Influence of arc lenght on dilution and weld bead geometry of Ni-based alloy using GTAW process with cold wire feed

Abstract

The Ni-Cr-Mo alloys are an important class of materials because of its very good pitting, crevice, stress corrosion cracking and wear resistance. However, in some cases the high cost of the Ni-based alloy justifies the application of this material as coating of equipments manufactured with carbon steel. In weld overlay it is essential to control the chemical composition of weld metal, reducing the dilution with substrate during fusion. This is important to avoid secondary phase precipitation, to minimize the hot cracking tendency and to guarantee a good performance in service. The present work evaluates the influence of arc length on dilution and weld bead geometry in dissimilar weld overlay. Bead on plate welds were prepared on C-Mn steel plate (ASTM A516-Gr. 60) using Ni-based filler metal (Inconel 625)deposited by the gas-tungsten-arc-welding (GTAW) process with cold wire feed. Three arc lengths were used in this work: 6, 10 and 14 mm. The ANOVA results indicated that the arc length influences all geometric characteristics except reinforcement. The influence of arc length on width, although statistically significant, it did not show to be important. When the arc length was increased from 6 to 10 mm, a decrease of penetration was observed, but the effect of reduction was not reached when the arc length was increase to 14 mm. In addition, it was possible to reduce significantly the dilution level when the arc length was increased from 6 to 10 mm. However, as well as penetration, when the arc length was increased from 10 to 14 mm did not present a practical benefit on the dilution level. It was possible to conclude that the arc length is an important welding parameter to control the dilution level in dissimilar weld overlay.