Although hard coatings like CrN are essential for increasing wear resistance, their poor substrate compatibility severely limits their engineering uses. The study achieves simultaneous formation of a Cr-N-Fe metallurgical interface and CrN coating through the deposition-nitriding composite strategy, resulting in a significant improvement in coating adhesion. Fretting wear experiments showed that the 40CrNiMo+Cr+PN exhibited a wear rate of 1.48×10 -7 mm 3 N -1 m -1 under a high load of 50 N, which was 7.68 times lower than the 40CrNiMo. The exceptional fretting wear performance originates from the generation of an excellent metallurgical interface, and the in-situ formation of a Cr 2O 3/CrN heterostructure under wear. This heterostructure, composed of in-situ formed Cr 2O 3 nanoparticles during wear and the CrN coating, facilitates wear-resistant lubrication and synergistic strength-plasticity effects, thereby reducing friction and wear. This study provides important insights into the fretting wear behavior of deposition-nitriding CrN coatings and provides important guidance for the application of protective coatings on spline shafts.