Effects of ultrasonic surface rolling processing and plasma nitriding on the fretting wear behavior of Inconel 690TT

Inconel 690TT has been applied to steam generator for transport tube, which fretting wear (FW) will cause serious damage on it. In this work, the ultrasonic surface rolling processing (USRP), plasma nitriding (PN) and ultrasonic surface rolling processing combined with plasma nitriding process (USRP+PN) are applied for improving the fretting wear behavior of Inconel 690TT. The results show that a high fraction of grain boundaries is induced after the USRP. Compared to the untreated specimens, the surface hardness of specimen treated by the USRP, PN and USRP + PN increased by 191%, 295% and 348%, respectively. It can be attributed that the USRP can improve the surface hardness by the gradient nanostructure (GNS) layer, and the PN process can enhance the surface hardness by changing the chemical composition near the top surface. After the USRP, PN and USRP+PN, the wear volume decreased by 72%, 86%, 96%, respectively. It indicated that the surface fretting wear resistance by benign effect between processes can be arranged as USRP+PN > PN > USRP > untreated, which can provide a potential way to improve the surface fretting wear resistance of Inconel 690TT. •Gradient nanostructure layer is consisted by lamellar and equiaxial nano-grains.•After ultrasonic surface rolling and plasma nitriding, the hardness is increased.•Ultrasonic surface rolling specimen shows good surface fretting wear resistance.