Effect of Aluminizing and Laser Shock Peening Treatments on the High-Temperature Oxidation Resistance of AISI 321 Stainless Steel for Solar Thermal Power Heat Exchanger

• Aluminizing combined with laser shock peening (LSP) significantly enhances the high-temperature oxidation resistance of AISI 321 stainless steel at 620 °C. • The optimal oxidation resistance shifts from aluminized steel to LSP-treated steel after 144 hours, due to the formation of a protective α-Al2O3 film. • LSP-induced subgrain boundaries act as short-circuit paths for Al diffusion, promoting rapid nucleation of α-Al2O3 and improving oxidation resistance. • The combination treatment reduces the oxidation parabolic constant by up to 69.18% compared to aluminized steel and 36.36% compared to untreated 321 steel, offering a promising surface treatment for long service life in solar thermal heat exchangers.