We conducted a study on the surface compound modification of shot peening and pure carbon DLC coating to simultaneously meet the requirements of wear resistance and fatigue resistance of spline structure. The effects of surface compound modification were investigated on the surface morphology, residual stress profile, microstructure, and nano-indentation hardness of 16Cr3NiWMovNbE gear steel, and conducted a comparative study on fatigue performance. The results show that the surface compound modification inherits the surface morphology and compressive residual stress gradient of shot peening, while the surface residual stress is slightly smaller than that of shot peening. In addition, surface compound modification still reflects the characteristics of high hardness and high fracture resistance of DLC coatings. Under the bending load based on spline tooth root, compared to the original specimen, the fatigue life after shot peening, pure carbon DLC coating, and surface compound modification is increased by 3.68, 2.35, and 3.36 respectively. Although the compound modified surface still maintains the shot peening morphology with a increasing surface roughness and stress concentration coefficient, the 100 μm-depth compressive residual stress profile and the subgrain refinement layer introduced, as well as the hard surface layer with good load-bearing capacity, have played the role of fatigue strengthening.

Transmission engineering components need to fulfill requirements for adequate wear resistance and fatigue resistance, which are related to their surface properties. In this paper, we combined shot peening and nitrogen ion implantation to improve the surface properties of 16Cr3NiWMoVNbE gear steel. The average surface roughness decreased slightly after the ion implantation because of the high-speed impact of implanted ions having the surface etching role. The maximum compressive residual stress of the near-surface layer after the surface treatment increased by more than 11.8–15.9% compared with shot peening. The nitrogen ions diffused through the peening deformation channel, and the deformation degree and the implantation temperature were positively correlated with the diffusion process. The surface nano-hardness obtained by ion implantation after shot peening was increased by 124.4% compared to the AR state.