Fretting Wear, Rotary Bending and Ultrasonic Fatigue Properties of Aged Inconel 718 Alloy Subjected to Ultrasonic Nanocrystal Surface Modification Technique

Fretting is a progressively damage of materials, which occurs inevitably when two contacting surfaces exhibit small amplitude oscillatory motion. A combination of this motion and pressure exerted between interacting surfaces generates significant superficial stress concentration and fatigue of a material which can result in material removal and consequently can degrade fatigue lifetime of aerospace components which may lead to catastrophic failure or loss of functionality. In this study, the effectiveness of ultrasonic nanocrystalline surface modification (UNSM) technique was investigated on the fretting wear, rotary bending and ultrasonic fatigue properties of a nickel-based supper alloy Inconel 718 alloy, which was developed for use in rotating part in aerospace and gas turbine applications at various temperatures. Fretting wear, rotary bending fatigue and ultrasonic fatigue test results showed that the UNSM-treated specimens reduced the fretting wear and prolonged fatigue life of Inconel 718 alloy compared to those of the untreated specimens, which may be attributed to the fine grain structure, induced compressive residual stress and increased hardness.