Wagner coefficient of interaction between hydrogen and nickel in liquid steel

Abstract

The simplest model of the structure and interatomic interaction is applied to hydrogen solutions in liquid alloys of Fe – Ni system, which earlier (2019 – 2021) was used by the authors for nitrogen solutions in alloys of Fe – Cr, Fe – Mn, Fe – Ni, Ni – Co and Ni – Cr systems. The theory is based on lattice model of the Fe – Ni solutions. The model assumes a FCC lattice. In the sites of this lattice are the atoms of Fe and Ni. Hydrogen atoms are located in octahedral interstices. The hydrogen atom interacts only with the metal atoms located in the lattice sites neighboring to it. This interaction is pairwise. It is assumed that the energy of this interaction depends neither on the alloy composition nor on the temperature. For simplicity it was assumed that liquid solutions in the Fe – Ni system are perfect. Within the framework of the proposed theory an expression is presented for the Wagner coefficient of interaction between hydrogen and nickel in liquid steel. The right-hand part of the appropriate formula is a function of the ratio of the Sieverts law constants for hydrogen solubility in liquid iron and in liquid nickel. The values of these constants for a temperature of 1873 K are taken equal to K′H(Fe) = 0,0025, K′H(Ni) = 0,0040 wt. %. At the same time, an estimate was obtained for the Wagner coefficient of interaction between hydrogen and nickel in liquid steel  εHNi = –0,54. This corresponds to the value of the Langenberg interaction coefficient eHNi = –0,002, wich is very close to the experimental estimate eHNi = –0,0022.