Synergistically enhanced DLC wear resistance via interfacial reconstruction and multiscale optimization of H13 steel

To overcome the critical challenges of interfacial stress mismatch and coating delamination in H13 steel subjected to extreme prolonged high-load service conditions, this research pioneered an advanced surface engineering strategy integrating combining ultrasonic surface rolling peening (USRP) pretreatment and diamond-like carbon (DLC) film. The interface engineering approach achieved a breakthrough in wear resistance through microscale mechanical interlocking architecture and chemical bonding optimization. The results demonstrated that USRP induced a hardness gradient layer with a depth of 900 μm on the H13 steel surface, increased the surface microhardness by 17.18 %, additionally, a U-shaped micro-textured array with a width of approximately 100 μm was introduced, these microstructures serve to increase the interfacial contact area, thereby altering the bonding mode between the coating and the substrate from pure chemical bonding to a “chemical-mechanical synergistic anchoring” mode. XPS analysis confirmed that USRP pretreatment promoted the enrichment of Cr₂O₃ and Fe₂O₃, improved the covalent bonding of Cr-C bonds, and significantly altered the interfacial chemical environment, which effectively alleviated the interfacial thermal stress mismatch problem. elevating the interfacial surface energy from 31.46 mJ/m² to 36.18 mJ/m². Consequently, the DLC coating adhesion strength (Lc₂) increased from 1.67 GPa to 5 GPa, an 86.66 % improvement. Friction tests revealed that the pretreated DLC exhibited a wear rate of only 6.827 × 10⁻⁸ mm³/N·m during 10-h prolonged wear, a 42 % reduction compared to the untreated coating. This work reveals the optimization mechanism of DLC coating cross-section under USRP pretreatment, which provides a theoretical basis for long time wear resistance of DLC.