# Study the Effect of Heat Treatment on the Corrosion Resistance of AISI 347H Stainless Steel

## TL;DR

This study shows that heat treatment improves the corrosion and oxidation resistance of AISI 347H stainless steel by refining its microstructure and enhancing passive film stability.

## Contribution

The study systematically demonstrates how solution treatment improves corrosion resistance in AISI 347H stainless steel through microstructural refinement and passive film stabilization.

## Key findings

- Solution treatment dissolves coarse Nb-rich precipitates and refines the austenitic microstructure.
- Treated samples show lower corrosion current density and higher charge transfer resistance.
- Oxidation is suppressed by the formation of Cr-rich scales with Nb oxides, limiting diffusion pathways.

## Abstract

AISI 347H stainless steel is widely used in high-temperature environments due to its excellent creep strength and oxidation resistance; however, its corrosion performance remains highly sensitive to thermal oxidation, and the effects of thermal history on its passive film stability are not yet fully understood. This study addresses this knowledge gap by systematically investigating the influence of solution treatment on the corrosion and oxidation resistance of AISI 347H stainless steel. The specimens were subjected to solution heat treatment at 1050 °C, followed by air cooling, and then evaluated through electrochemical testing, high-temperature oxidation experiments at 550 °C, and multiscale surface characterization techniques. The solution treatment refined the austenitic microstructure by dissolving coarse Nb-rich precipitates, as confirmed by SEM and EBSD, and improved passive film integrity. The stabilizing effect of Nb also played a critical role in suppressing sensitization, thereby enhancing resistance to intergranular attack. Electrochemical measurements and EIS analysis revealed a lower corrosion current density and higher charge transfer resistance in the treated samples, indicating enhanced passivation behavior. ToF-SIMS depth profiling and oxide thickness analysis confirmed a slower parabolic oxide growth rate and reduced oxidation rate constant in the solution-treated condition. At 550 °C, oxidation was suppressed by the formation of compact, Cr-rich scales with dual-distributed Nb oxides, effectively limiting diffusion pathways and stabilizing the protective layer. These findings demonstrate that solution treatment is an effective strategy to improve the long-term corrosion and oxidation performance of AISI 347H stainless steel in harsh service environments.