Corrosion Behavior of Nitrogen-Containing Low-Nickel Weld Cladding in KCl-MgCl2 Eutectic Molten Salt at 900 °C

Abstract

In this paper, the element nitrogen (N) is used to partially replace the element nickel (Ni) in flux-cored wire. A 44%Ni-24%Cr-0.18N nitrogen-containing low-nickel flux-cored wire with excellent corrosion resistance is prepared. The corrosion behavior of nitrogen-containing low-nickel weld cladding and Inconel 625 weld cladding in 40 KCl + 60 MgCl2 (wt%) molten salt at 900 °C is studied. The results show that the selective dissolution of Cr occurs in both weld claddings. The corrosion resistance of the 44%Ni-24%Cr-0.18N nitrogen-containing low-nickel weld cladding is better than that of the Inconel 625 weld cladding. The reason is that added N can react with H+ in molten salt to generate NH4+, remove corrosive impurities of MgOH+ in molten salt and change the corrosion environment. N preferentially combines with Cr to form Cr2N, reduces the diffusion precipitation of Cr and improves the corrosion resistance.

Study on Hot Corrosion of Low-Nickel Cladding Metals Containing Nitrogen in K2SO4-MgSO4 Binary Molten Salt

“…After the formation of the Cr 2 O 3 oxide film, the Cr element on the surface of the deposited metal undergoes volume expansion, and the expansion coefficient of the formed oxide film is inconsistent with that of the deposited metal. Therefore, as the stress in the alloy matrix increases, it will crack and fall off, causing local Cr-deficient areas [17]. On the unprotected surface of the deposited metal, S and O elements can enter the interior of the deposited metal along this area, which is consistent with the distribution of S elements found inside the deposited metal in Figure 4e.…”