Avaliação da diluição de aço inoxidável ER308LSi depositado em aço carbono SAE1020 via manufatura aditiva por deposição a arco

Abstract

Wire arc additive manufacturing (WAAM) has become a viable alternative to produce medium and large-scale metallic components, offering high deposition rates and reduced material waste. When applied to dissimilar material pairs, however, the mixing between filler metal and substrate during weld pool formation changes the first layers’ chemical composition, affecting the microstructure and mechanical properties. This work aims to study the chromium and nickel dilution along the build direction in an ER308LSi austenitic stainless steel preform deposited on carbon steel substrate by WAAM. The preform cross-section was analyzed by macrography, optical microscopy, scanning electron microscopy with energy dispersive X-ray spectroscopy microanalysis and Vickers microhardness testing. The penetration of the first bead into the substrate was 2.8 mm. The compositional profile revealed an abrupt transition at the interface, followed by a plateau of constant composition extending over 3.0 mm, with average contents of 13.22 % chromium and 5.99 % nickel, and by progressive enrichment up to 17.86 % chromium and 7.83 % nickel at the top of the preform. Dilution estimated by mass balance ranged from 32 to 46 % in the first bead, decreasing to between 9 and 30 % at the top. The microhardness profile followed the compositional profile, with a marked increase in the diluted region, attributed to the loss of austenite stability caused by the reduction in nickel content and the consequent formation of martensite, an interpretation supported by the Schaeffler diagram. It was further observed that the microstructural boundary, defined by the hardness drop, lies approximately 0.9 mm above the compositional boundary, a lag consistent with the fact that austenite stability is governed by nickel content.