Estudo da soldabilidade de consumíveis de ligas a base de níquel em soldagem dissimilar com aço carbono por meio do ensaio Trans-Varestraint

Abstract

Nickel-based alloys are advanced engineering materials known for their corrosion resistance, good mechanical properties at high and low temperatures, and are widely used in the aeronautical, chemical, energy, and oil & gas industries, among others. Nickel-based alloys are often not used to manufacture massive parts due to their high cost. These alloys have been widely used as claddings and for dissimilar joint welding with C-Mn and low alloy steels. Some nickel-based alloys are highly susceptible to solidification cracks in their pure state. Dissimilar welding leads to changes in chemical composition, can affect the microstructure and metallurgical features, therefore, the analysis of the interaction of the materials involved in the process is necessary. The introduction of new chemical elements to the fusion zone in the dissimilar welding with nickel-based alloys can result in a change in the susceptibility to solidification crack. The objective of this study is to evaluate the weldability of dissimilar welds between the Inconel 625 and the Hastelloy C-276 nickel-based alloys deposited on the ASTM A36 and the AISI 1045 carbon steels carried out by the GMAW process, using the Trans-Varestraint weldability test. For this purpose, the influence of welding heat input, dilution level, and the kind of base metal on the weldability of the Ni-based alloys were evaluated. Based on the Trans-Varestraint test results, the Hastelloy C276 as filler metal on the AISI 1045 steel base metal shown more susceptible to cracking than all other pairs tested. The thermodynamic simulation contradicts the result of the Trans-Varestraint test, pointing that the alloy Inconel 625 has got the worse weldability. The contradiction observed in both analyzes is explained through microstructural analysis, indicating the occurrence of backfilling in the welds performed using the wire of Inconel 625. In conclusion, the results indicate that dissimilar welding induces the precipitation of secondary phases deleterious to the weldability of the wire/base metal set, which can be further reduced depending on the chosen materials. The Hastelloy C276 alloy showed a significant drop in weldability with the change of the base metal, with AISI 1045 steel being the most detrimental. The differences obtained between the Trans-Varestraint test and the simulations using Inconel 625 alloy can be explained by the presence of the backfilling effect.