Surface state of Inconel 718 ultrasonic shot peened: Effect of processing time, material and quantity of shot balls and distance from radiating surface to sample

► As USP processing time increases more compressive surface stresses are induced until a saturation level is reached. ► The distance between part and radiating surface notably influences the surface state. ► A greater number of shot balls leads to less impacts of lower energy on the part surface. ► Surface nanocrystallization can only be achieved with large impacting energies of the balls.