First principles, thermal stability and thermodynamic assessment of the binary Ni–W system

Abstract

First principles, thermal stability and thermodynamic assessment of the binary Ni-W systemThe Ni-W binary system was assessed using critically evaluated experimental data with assistance from first principles analysis and the CALPHAD method. The solution phases (liquid, fcc-A1 and bcc-A2) were modeled using the substitutional regular solution model. The recently discovered Ni 8 W metastable phase was evaluated as Fe 16 C 2 -like martensite with three sublattices, and shown to be possibly stable according to first principles calculations. Ni 8 W was also modeled as an interstitial compound, but the model is not good because the solubility of tungsten in nickel is very low, especially at low temperatures. There is no experimental evidence for such low solubility. The other binary compounds Ni 4 W and Ni 3 W were assessed as stoichiometric ones. Compared independent experimental and first principles data agree well with the calculated phase diagram using updated thermodynamic parameters.

Comment on the paper "Experimental investigation of the Ni–V–W ternary phase diagram", Calphad: Comput. Coupling Phase Diagrams Thermochem. 76 (2022) 102384

“…The results on Ni-W system have been confirmed since then by several authors, see e.g. [4][5][6][7]. In particular, in Ref.…”

“…In particular, in Ref. [6], Isomäki et al, made a complete review (see references therein) and reach the same conclusions.Any discussion is absent from the paper of Meifang Tang et al to rebute the arguments developed in previous literature. The statement 'In their (Isomäki's) assessment, the WNi phase is considered to be metastable' is misleading.…”

“…In particular, in Ref. [6], Isomäki et al, made a complete review (see references therein) and reach the same conclusions.…”

Evaluation of Tungsten—Steel Solid-State Bonding: Options and the Role of CALPHAD to Screen Diffusion Bonding Interlayers

“…CALPHAD (CALculation of PHAse Diagram) modelling, which plays a crucial role in understanding complex materials' systems under different conditions, has been leveraged for a better understanding of tungsten steel joining [22]. CALPHAD is a widely used computational approach in materials science to predict phase equilibria in multi-component systems [23]. It utilizes thermodynamic databases containing Gibbs energy data for phases as a function of temperature, pressure, and composition.…”

Aqueous colloidal processing of W and WC-based composites, sintering and mechanical properties at high temperature

“…Ni6W, Ni8W or the richer W-based alloy NiW2(Isomäki et al, 2017), although the existence of this last species was already reported by Poulsen in the 1970s(Poulsen, Rubaek and Langer, 1974). They also indicate the technique(s) used to characterize these species.…”