Detection of Sensitization for 600 Alloy and Austeni ic Stainless Steel by Magnetic Field Sensor

The Ni base alloy and austenitic stainless steel s how usually paramagnetic property, whereas they transform into ferromagnetic along grain boundaries where sensitization occurs; this indicates a potential of n n-destructive evaluation using magnetic measurement for sensitization. Here, as a feasibility study for application of non-destructive evaluation for sensitization using magnetic measurement, heat treated Ni base alloy and austenitic stainless steel were s canned by a magnetic field sensor and the changes in magnetization were obtained nondestructively. When the specimens were magnetized with the direction perpen dicular to their surface before measurement, behaviour of changes in the magnetic f lux density perpendicular to the surface are consistent with the results of magnetiz ation obtained by the Vibrating Sample Magnetometer. The change in the flux density ear the surface of specimen is related to the degree of chromium carbides progress ing sensitization. The obtained results suggest that scanning with magnetic field s ensor is effective to assess sensitization due to heat treatment for Ni base all oy and austenitic stainless steel.