Investigating the Impact of Heat Treatment on the Mechanical, Corrosion, and Heat-Transfer Characteristics of Thermal Oxide Layers on SS304

Abstract

Despite inherent chemical and physical stability of stainless steel, the significantly lower productivity of energy compared to energy usage still necessitates research in harsh environments that demand high material performance under challenging condition. This study explores the formation and characterization of mechanical properties, corrosion, and heat-transfer behaviors for thermal oxide layers on SS304 through various heat treatment conditions. The heat treatment at low temperature (500 °C) formed thin oxide layers with few tens of nanometers (S-500), delivering to superior mechanical properties, measured by nanoindenter. However, the thin layers of S-500 show rapid corrosion behaviors in NaCl solution, investigated by linear sweep voltammetry polarization curves. In contrast, the thick oxide layers of S-700 with the thickness of 2.5-3.5 µm grown at high temperature (above 600 °C) showed low mechanical properties but superior corrosion resistance. The difference between heat treatment conditions derive to diverse oxide compositions from SS304 substrate, particularly, Cr₂O₃ at 700 °C. The Cr₂O₃ provided high corrosion resistance, but it reduced thermal conductivity due to its intrinsic properties.