Fatigue Properties of Ti17 Alloy Strengthened by Combination of Electric Spark Treatment with Ultrasonic Surface Treatment

The surfaces of Ti17 alloy were strengthened by an electric spark treatment (EST), then an ultrasonic surface treatment was used in order to improve the fatigue life. The surface morphology was observed by SEM. The surface residual stress was analyzed by a X-ray diffractometer. Tension-tension fatigue tests were carried out in a HT-100 fatigue testing machine at 350 °C. The results show that the surface roughness and the residual stress are reduced for the specimens after the ultrasonic treatment. The fatigue life of the specimens strengthened by ultrasonic treatments is about twice that of the specimens treated by EST only. The fatigue life of the specimen strengthened by YG8 electrode EST combination with ultrasonic treatment is the longest.