Tribological characteristics of ultrasonic rolling extrusion strengthened 316L and CFRPEEK under water lubrication conditions

To improve the hardness and wear resistance of 316L stainless steel, which cannot be strengthened through conventional heat treatment, an ultrasonic rolling extrusion method is proposed for surface strengthening. Ultrasonic rolling extrusion experiments are conducted on 316L under different process parameters. To obtain the process parameters for maximum surface hardness, an optimization and prediction model is established using the response surface methodology. The improvement in the tribological performance of 316L is characterized and analyzed through friction and wear tests, metallography, and SEM. The results indicate that the order of process parameters influencing surface hardness is: Static pressure > Feed rate > Spindle speed > Amplitude. The surface hardness of the strengthened 316L increases by 43.6%, and the depth of the refined grain layer reaches 130 μm. In the water-lubricated ring-on-pin friction and wear tests, the friction coefficient and wear volume of the strengthened 316L decrease by 42.9% and 23.3%, respectively. The wear volume of the paired CFRPEEK also significantly reduces. Additionally, The fatigue wear and abrasive wear resistance of 316L after strengthening is significantly improved. This study demonstrates the effectiveness of the ultrasonic rolling extrusion strengthening method, which is of significant importance for the design and application of water-lubricated friction pairs.