Application of crosswise repetitive ultrasonic nanocrystal surface modification treatment to Inconel 690 alloy: Efficiency of single-path and multi-paths

In this study, the efficiency of crosswise repetitive ultrasonic nanocrystal surface modification (CR-UNSM) treatment on surface characteristics, tribological and fatigue properties of single and multi (double, triple, quadruple and quintuple) treated Inconel 690 alloy was investigated. All the CR-UNSM-treated specimens demonstrated better tribological and fatigue performance in comparison with the untreated specimen. Quintuple CR-UNSM-treated specimen demonstrated the lowest coefficient of friction (COF) and specific wear rate (SWR) among untreated and other CR-UNSM-treated specimens, while triple CR-UNSM-treated specimen was found to be the most effective in terms of fatigue performance. The surface roughness of Inconel 690 alloy was signifi-cantly reduced after single CR-UNSM treatment, afterwards it was gradually roughened with increasing the number of CR-UNSM treatment. The surface hardness along with hardened surface layer and also compressive residual stress (CRS) were increased with increasing the number of CR-UNSM treatment. Every CR-UNSM treatment was capable of refining coarse grains into nano-scale grains, where the higher number of CR-UNSM treatment the thicker nanostructured surface layer (NSL) and the finer grain size.

Automated summary

This study investigated the effects of crosswise repetitive ultrasonic nanocrystal surface modification (CR-UNSM) treatment on the surface characteristics, tribological, and fatigue properties of Inconel 690 alloy. The results showed that all the CR-UNSM-treated specimens exhibited improved tribological and fatigue performance compared to the untreated specimens. The triple CR-UNSM-treated specimen showed the best fatigue performance, while the quintuple CR-UNSM-treated specimen had the lowest coefficient of friction and specific wear rate. The surface roughness of the alloy decreased after a single CR-UNSM treatment but increased gradually with more treatments. The surface hardness, hardened surface layer, and compressive residual stress also increased with the number of CR-UNSM treatments. Each CR-UNSM treatment was able to refine coarse grains into nano-scale grains, resulting in a thicker nanostructured surface layer and finer grain size with more treatments.