Construção de revestimentos modificadores de superfície por processo de soldagem a arco elétrico com eletrodo revestido (SMAW)

Abstract

This work investigated the surface modification of A36 steel by SMAW welding using fluxes enriched with boron and ferro-niobium carbide (Fe-NbC) in dry and wet routes, focusing on the improvement of properties related to microhardness. The methodology involved visual inspection, macroscopic analysis to determine the dilution rate, microstructural characterization of the fusion zone, heat-affected zone, and base metal, as well as Vickers microhardness tests. The results showed sound weld beads and dilution rates with discrete variations, presenting a tendency for dilution rate reduction with boron and a slight increase with Fe-NbC, with greater stability in dry welding. The microstructures revealed that Fe-NbC favored the formation of dendritic columns and NbC carbides, while boron promoted B₄C carbides and microstructural refinement, with agglomeration at higher concentrations. Microhardness showed moderate variations, with boron being the most effective agent in hardening, approaching the values of the reference sample. The HAZ maintained uniform behavior, and the base metal preserved its original microstructure. It was concluded that boron stood out as the element with the greatest impact on the final performance of the coatings, both by reducing dilution and increasing hardness.