Achieving superior fretting fatigue resistance of nickel-based single crystal superalloy tenon by shot peening

• 0.25 mmA shot peening intensity made the nickel-based single crystal superalloy have the longest fretting fatigue life. • Shot peening and fretting fatigue formed a three-layer heterogeneous gradient nanostructure on the surface. • The shot peening strengthening mechanism was a synergistic strengthening mechanism of work hardening, compressive residual stress, surface morphology and heterogeneous gradient nanostructure. This study systematically investigated the elevated fretting fatigue (FF) behaviors of nickel-based single crystal (NBSC) superalloy tenons subjected to different shot peening (SP) intensities and FF temperatures. The results revealed that the nano-hardness of the SP surface was 7.13 ∼ 7.98 GPa (0.25 and 0.35 mmA), which was 28.70% ∼ 44.04% higher than that of as received (AR) NBSC superalloy. The compressive residual stress (CRS) on the SP surface reached −1044.03 ∼ -1083.67 MPa, and the maximum CRS was −1358.59 MPa at about 30 μm from the SP surface (0.35 mmA). The FF lives of SP-0.25 tenons were the longest at both temperatures, which was 22.02 and 18.70 times higher than that of AR tenons, respectively. The increase in temperature had the least effect on the FF lives of SP-0.35 tenons, which was attributed to a sufficiently large and deep CRS field. During the FF test, the SP surface evolved into a three-layer heterogeneous gradient nanostructure, which suppressed FF crack initiation and propagation. The findings provided essential insights to well understand the strengthening mechanism of NBSC superalloy and guide its fretting fatigue resistance design.