Enhanced wear resistance of 304 stainless steel by an improved method based on ultrasonic strengthening grinding process and PTFE coating

The wear resistance of the friction interfaces under heavy loads is a critical factor for the friction pendulum bearing (FPB) in civil engineering. Although the ultrasonic strengthening grinding process (USGP) had demonstrated improvement in the wear resistance of metallic components, the friction coefficient was relatively high, exceeding the acceptable range of FPB. This work presented an improved method to enhance the wear resistance of 304 stainless steel in terms of the application scenario of FPB in civil engineering. Firstly, the surface of the 304 stainless steel was subjected to USGP treatment with a high-energy impact of multiphase abrasive. Subsequently, the USGP-treated surface was deposited with polytetrafluoroethylene (PTFE) by spraying. Finally, the surface microhardness increased from 212.6 HV to 543.2 HV after USGP treatment, reflecting an increase of 155.5% compared to the untreated sample. Noticeably, a great amount of austenite was transformed into ultrafine martensite in the topmost layer. As a result, the improved method demonstrated a significant enhancement in the wear resistance of 304 stainless steel, with the friction coefficient and wear grooves reducing markedly as compared with the samples treated by other processes. The synergistic effect of the composite microstructure, which consisted of a gradient-structure reinforced layer, micro-pits, and PTFE coating, accounted for the enhanced wear resistance. Our findings provided new insights into improving the wear resistance of 304 stainless steel used for PFB friction interfaces in civil engineering application scenarios.