Análise da solidificação e transformações no estado sólido através de simulações termodinâmicas e termogravimetria em ligas de níquel produzidas in situ por manufatura aditiva.

Abstract

Alloy design is currently a strategic tool in materials engineering, enabling the development of alloys with optimized properties for welding and additive manufacturing applications. In this context, nickel-based alloys stand out due to their exceptional combination of mechanical properties, thermal stability, and corrosion resistance. As an alternative for processing these materials, duble-wire GMAW (Tandem) technique has been proposed. This process allows for the simultaneous melting of different filler metals, facilitating in-situ alloy synthesis. Furthermore, the flexibility of the process enables precise adjustment of the resulting chemical composition by controlling the melting rates. In this work, AWS ERNiCrMo-3 (INCONEL 625) and AWS ERNiCrMo-4 (HASTELLOY C276) filler metals were co-melted to produce in situ alloys, with the resulting compositions based on the share of each commercial alloy: alloy A (50% 625 / 50% C276), alloy B (35% 625 / 65% C276), and alloy C (65% 625 / 35% C276). To analyze the solidification behavior, Scheil-Gulliver simulations were performed using Thermo-Calc® and JMatPro® software.Additionally, four conditions were simulated to evaluate the stability of the formed phases: (a) with σ-phase and with carbon inclusion; (b) without σ-phase and with carbon inclusion; (c) with σ-phase and without carbon inclusion; and (d) without σ-phase and without carbon inclusion. The simulations of the in-situ alloys indicated the formation of phases such as σ, μ, δ, P, M6C, MC, and Laves, in addition to the FCC-Ni (γ-Ni) matrix.Complementing the solidification analysis, solid-state transformations occurring during both cooling and aging heat treatments were investigated. For this purpose, TTT and CCT diagrams were simulated using JMatPro® for in-situ alloys A, B, and C, which indicated the formation of phases such as P, μ, σ, γ’’, and δ, as well as M₆C and M23C6 carbides.To validate the thermodynamic simulations, DSC scans were conducted, in which two peaks were identified during solidification, and no thermal events were observed during cooling below the Tsolidus.