Magnetic evaluation of creep in modified 9Cr–1Mo steel

Magnetic Barkhausen emissions (MBE) and magnetic hysteresis loop techniques have been used to correlate the magnetic properties with creep behaviour in modified 9Cr–1Mo steel. Formation of massive carbides like M23C6, Laves phase (Fe2Mo) and Z-phase are the cause of creep failure in the present material. The root mean square voltage of MBE signal increased from the secondary stage of creep. This was attributed to the growth of carbides. Microcracks generated by massive and brittle precipitates induced demagnetizing fields that restricted domain wall movement, resulting in continuous reduction of remanence during creep.