Effects of ultrasonic surface rolling processing on microstructure and wear properties of high-carbon high-chromium steel

The main purpose of this work was to study the dissolution behavior of carbides and the microstructure evolution in high-carbon high-chromium steel during ultrasonic surface rolling processing (USRP), as well as the wear properties of the samples before and after USRP. The microstructural features of the surface deformed layer were characterized by some microscopic analysis methods (SEM, TEM, EBSD, XRD and microhardness analysis). The wear properties of the untreated and treated samples were tested using a reciprocating tribometer. Results indicated that the long rod-shaped primary carbides (PCs) can be sufficiently fractured and dissolved during U SRP, resulting in the formation of fine microstructure at the surface adjacent region. During USRP, the equiaxed grains were formed due to the continuous dynamic recrystallization (CDRX), and the fraction of recrystallized grains increased with the decrease in depth. The dissolution of hard carbides and the occurrence of CDRX during U SRP limited the further improvement of hardness. However, the fine microstructure of the USRP treated sample helped to inhibit the initiation and propagation of cracks, which benefited the wear resistance of the material.