One-step construction of CrN coating and Cr-N-Fe metallurgical interface via deposition–nitriding strategy for enhanced fretting wear resistance of 40CrNiMo

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 mm³ $·$ 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 Cr₂O₃/CrN heterostructure under wear. This heterostructure, composed of in-situ formed Cr₂O₃ 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.