PSI - Issue 81

Anatolii Klymenko et al. / Procedia Structural Integrity 81 (2026) 470–477

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Singh (2001), Yu et al. (2005), Bauer et al. (2013), Kuravi et al. (2013), Sarvghad et al. (2017a) and Tomota et al. (2014). It resists oxidation at very high temperatures up to 1250 °C, even under severe conditions such as cyclical heating and cooling. The alloy is readily formed, machined, and welded. These properties enable its use as a structural material in various industries, including petrochemical, oil and gas, nuclear, power generation, industrial furnaces, gas turbines, insulating cans in ammonia reformers, strand annealing and radiant tubes, combustion chambers, and thermal energy storage, among others. In most metals exposed to reaction environments involving molten salts at high temperatures, there is a tendency to form intermetallic compounds, was reported by Ravindran et al. (1996) and to oxidize over a wide temperature range (in particular due to sensitization as a result of heating), and its rate and morphology are important factors for predicting and evaluating the service life of equipment materials and the performance of the production cycle as a whole, was reported by Sarvghad et al. (2017b, 2017c), Tomota et al. (2014), and Guo et al. (2015)). Inconel alloys, in addition to residual stresses in the lattice, are characterized by brittle intergranular fracture caused by oxygen penetration through grain boundaries (Sarvghad et al. (2017b), Pang et al. (1994), Pfaendtner et al. (2001)). Furthermore, increased susceptibility of alloys with high chromium content to corrosion at grain boundaries, with the formation of uniformly distributed voids in the microstructure, is attributed to surface chromium carbides along with high carbon content (Sridharan et al. (2013)). According to the authors Bauer et al. (2013), Sridharan et al. (2013) and Goods et al. (2004), chromium depletion followed by chromium oxidation and cavity formation is caused by substitution diffusion – chromium diffusing from the interior of the alloy toward the surface, driven by the concentration gradient, accompanied by vacancy migration and coalescence. It is also known that alloying elements (Cr, Al, Si, Nb) from molten salts at elevated temperatures contribute to the formation of diffusion-barrier self-regenerating surface protective oxide films that prevent further oxidation by limiting oxygen access to the metal, as shown by Sarvghad et al. (2017b, 2017c), Sridharan et al. (2013) and Young (2008). At the same time, salts penetrate the metal sample during immersion, and their strong fluxing action can destabilize the deposit, but the oxide layer itself can be stable, though not completely protective, given the relatively high solubility of chromium (Sarvghad et al. (2017b)). With regard to changes in the mechanical properties of steel when interacting with heavy metal melts, the authors Yas’kiv et al. (2016) highlight the influence of the environment on the ability to undergo plastic deformation at elevated temperatures, while a decrease in the plasticity of materials at operating temperatures leads to a decrease in their resistance to brittleness. As shown by Klymenko et al. (2022, 2024), the dynamics of corrosion rate changes in stainless steel – accompanied by transformations in the structure and composition of corrosion products – from a homogeneous, dense layer to a two-layer structure with distinct layers, tend to decrease in molten salts (lead melt) at high temperatures over time. This process is associated with the formation of surface protective oxide films. Additionally, carbides tend to coagulate on the base metal and precipitate along grain boundaries and rolling lines. The microhardness of the formed surface corrosion products significantly exceeds that of the base metal. The following general properties and characteristics of Inconel alloys are distinguished in terms of their corrosion resistance under operating conditions at elevated temperatures (Iqbal et al. (2025)): exceptional corrosion resistance, both in acidic environments (deep wells for crude oil and natural gas extraction) and against stress corrosion cracking, pitting and crevice corrosion, ensuring increased structural integrity and durability; extremely high strength, necessary for operation under elevated temperatures and significant mechanical loads; excellent wear resistance, necessary to prevent degradation of components exposed to prolonged exposure to corrosive substances under high-temperature conditions. The purpose of this work was to study the degradation of Inconel 601 alloy in molten lead at temperatures of 450°C and 650°C, as well as to study the kinetics of corrosion product formation in molten lead to generate and accumulate experimental data for subsequent comparative analysis of the effectiveness of various alloys as structural materials under the relevant operating conditions. The results obtained in the presented materials are a continuation of the authors' work (Klymenko et al. (2022, 2024)) on determining the corrosion resistance of some nickel-chromium alloys in a static lead melt at elevated temperatures and a comparative analysis of their characteristics. 2. Materials and methods The research was conducted on the nickel alloy Inconel 601 with the following chemical composition: 13.90% Fe, 24.18% Cr, 60.29% Ni, 1.21% Al, 0.42% Ti. The chemical composition of the molten lead was 99.99% Pb. The sample surface was cleaned with sandpaper with a medium grain size of 180WPF, and metal dust was cleaned with filter paper, followed by washing both off-running and distilled water and degreasing with an ethyl alcohol solution. To determine the corrosion rate, both the prepared samples and the samples after testing were weighed on an analytical balance VLR-200 with measurement accuracy up to 0.00005 g. A corrosion rate was calculated by the weight loss method: = 8,76∙∑ ∆ ∙ , (1) where ∑ ∆ ∙ is average corrosion rate by weight loss, g/(m 2 ∙ h) is corrosion rate in units of penetration, mm/year 8,76 is conversion coefficient is metal density, g/m 3 ∆ is sample mass loss, g is surface area of the test sample, m 2 is test duration time, h .