Changes of magnetic hysteresis properties due to creep damage in martensitic stainless steel

Measurements of magnetic minor hysteresis loops have been performed in martensitic stainless steel subjected to tensile creep test at 120 MPa and 873 K. The minor-loop coefficients as well as coercivity, which are indicators of internal stress, sharply increase at the primary creep and show a very slow increase at the secondary creep, followed by the steady increase at the ternary creep. A good correlation of the coefficients with creep strain clearly shows that magnetic method using minor hysteresis loops can be a possible technique for nondestructive evaluation of creep damage in the steels. (author)