Raman Thermometry for Thermal Characterization of Deposits Formed on Steel AISI SAE 316L in H ₂ S–O ₂ –N ₂ Atmosphere

Austenitic stainless steels are widely used in high‐temperature refining operations because of their corrosion resistance and mechanical stability, which arise from thermodynamically stable surface oxides. This work analyzes the thermal properties of surface layers formed on AISI 316L under simulated N 2 H 2 SO 2 atmospheres at 300–400 °C. Steel coupons are exposed for 12–36 h; morphology and composition are characterized by scanning electron microscopy/energy dispersive x‐ray spectroscopy, and thermal conductivity ( K ) and interfacial thermal conductance ( G ) are quantified by noncontact micro‐Raman thermometry. Spinel chromite (FeCr 2 O 4 ), Cr 2 O 3 , Fe 3 O 4 , Fe 2 O 3 , and iron sulfides are identified, with stratification depending on atmosphere and exposure time. A relationship is established between O 2 content and both K and G of the formed layers using noncontact micro‐Raman thermometry. Compared with oxidation‐only conditions, oxide/sulfidation layers exhibit systematically lower K and G , indicating improved thermal insulation and potential benefits for controlling parasitic heat transfer in refinery units handling sulfurous heavy crudes. The results link crystallinity and defect density (e.g., oxygen vacancies) with heat transport, supporting micro‐Raman thermometry as a sensitive probe of thin‐layer thermal behavior in complex multiphase scales.