Spring washers are normally made out of spring steel and are hardened to HV 430 to 530 and are used along with almost every externally threaded fastener. Due to their Spring action, they give a locking effect to the tightened fastener, when fastened with Spring washer.
Spring Lock Washers are of many types, most common one being the helical split washer. A ring split at one point and bent into a helical shape. This causes the washer to exert a spring force between the fastener’s head and the substrate, which maintains the washer hard against the substrate and the bolt thread hard against the nut or substrate thread, creating more friction and resistance to rotation.