Hard-Facing of Nuclear-Grade SS316LN Stainless Steel with FeCrNiMnV High-Entropy Alloy for Improved High-Temperature Wear and Molten Salt Corrosion Resistance

Abstract

The present work investigates the microstructure, texture, and microhardness evolution of FeCrNiMnV high-entropy alloy (HEA) as a weld overlay on SS316LN substrate. In the as-fabricated state, the HEA exhibits dendritic structures and localized agglomerates characteristic of rapid solidification, leading to moderate hardness (≈750 HV). Heat treatment at optimized conditions homogenizes the alloy, eliminates dendritic features, and enhances hardness to ≈1000 HV, whereas prolonged exposures induce secondary phase formation, agglomeration, and porosity, reducing hardness. Elemental distribution analysis reveales progressive diffusion-driven segregation, with vanadium- and chromium-rich clustering under extended treatments. Weld overlay of FeCrNiMnV on SS316LN produces a refined grain structure (≈8 μm) in the HEA with predominantly face-centered cubic phases and localized body-centered cubic regions, ensuring metallurgical compatibility. Microhardness across the interface shows a sharp transition from ≈225 HV in SS316LN to ≈1000 HV in HEA, attributed to grain refinement, lattice distortion, and solid solution strengthening. High-temperature tribological tests demonstrate load-dependent wear mechanisms, transitioning from adhesive and oxidative wear at lower loads to the formation of protective tribolayers at higher loads, significantly reducing wear rate and stabilizing friction. Molten salt corrosion studies further reveal time- and temperature-dependent degradation, with protective Fe–Cr oxides forming initially, followed by progressive cracking and spallation under prolonged exposure.