• LSP-CS treatment improved the fretting fatigue lifetime of GH4169 dovetail components at 500 °C by up to 494.9%, outperforming LSPwC (346.8%).
• Both LSPwC and LSP-CS introduce plastic deformation and residual compressive stress layers without significantly altering grain size, enhancing surface integrity.
• LSP-CS yields higher surface microhardness (+28.6%) and greater residual compressive stress (−404.3 MPa) compared to LSPwC (+20.5%, −306.5 MPa).
• The synergistic effect of the hardening layer and residual stress layer is the key mechanism for the improved fretting fatigue resistance at elevated temperatures.