A method is disclosed for treating an ultrasonic end effector or surgical blade. The method includes providing an ultrasonic end effector or surgical blade and inducing a residual compressive stress along at least one surface of the ultrasonic end effector or surgical blade. The residual compressive stress may be induced by peening the at least one surface. Such treatment improves the resistance of the ultrasonic end effector or surgical blade to fracture propagation and improves the fatigue life of the ultrasonic end effector or surgical blade. Ultrasonic surgical instruments comprising an ultrasonic end effector or surgical blade treated according to the method are also disclosed.
