A flat washer is generally used to increase the contact area between parts, protect them from damage by increasing the contact area; to reduce the pressure between the nut and the equipment. Commonly used flat washer materials are iron, carbon steel, stainless steel, copper, plastic, etc.
Thrust washers are used to support axial loads or lateral movements on a shaft and to prevent movement along that shaft. Its purpose is to prevent the thrust of a rotating object from causing wear to a stationary object. Thrust washers can be made of plastic, brass, bronze, stainless steel, graphite, or various other materials.