In this study, test materials with several different degradation levels were prepared by isothermal aging heat treatment at 630 degrees C up to 1820 h. Tensile and fracture tests were performed and those were compared with BI tests and DC potential drop method. These results show that normalized Brinell hardness agrees well with normalized tensile strength at the viewpoint of material degradation and the tensile strength and fracture toughness of degraded material can be determined by Brinell hardness or resistivity. (c) 2006 Springer Science + Business Media, Inc.