A fastening assembly includes a fastener having a head with an underside and an elongated shaft extending therefrom. The fastener constructed of at least one of a refractory metal and a superalloy. A washer includes a body with an upper surface and an opposing lower surface which defines opening portion for receiving the elongated shaft of the fastener therethrough. The upper surface of the washer forms diffusion bonds with the underside of the head of the fastener when the washer and the fastener are held in contact at temperatures in excess of 500° C.