Hi,
Spring washers are normally flat by the time the nut is fully torqued. At this time it is equivalent to a solid flat washer, and its locking ability is nonexistent. They have been found to actually loosen the bolt under vibration even faster than a joint with no washer.
Star washers are used for electrical grounding, sometimes used for spring action but mostly for locking action by biting into the mating surface. Although this washer does provide some locking action, it damages the mating surfaces. These scratches can cause crack formation in highly stressed fasteners, in mating parts, or both, as well as increased corrosion susceptibility.
Best wishes...