Degradation Evaluation of Mechanical Property for Modified 9Cr-1Mo Steel by Reversible Permeability

Abstract

The present work studies a nondestructive evaluation of the degradation of modified 9Cr-1Mo steel using a magnetic method based on the existence of the peaks of reversible permeability (RP) in the differential magnetization around the coercive force. The apparatus is based on detection of the voltage induced in a coil using a lock-in amplifier tuned to the frequency of the AC perturbing field. Results obtained for the reversible permeability and Vickers hardness on the aged samples showed the peak interval of reversible permeability (PIRP) and Vickers hardness decrease as aging time increased. The correlation between Vickes hardness and the PIRP could be used to evaluate degradation of modified 9Cr-1Mo steel.

Dynamic Coercivity of Tempered Ferritic Steel Subjected to Creep-Fatigue for Nondestructive Evaluation by Reversible Permeability

“…In addition, plastic deformation evolves lattice defects in materials such as vacancy and dislocation. It creates a significant increase in dislocation density and dislocation tangles are believed to be the pinning sites of domain wall movement [8,9]. This dislocation may exert a force on the domain wall and play the role of obstacles to the 180 Bloch wall movement.…”

“…With increased internal stress, the critical field required to move a domain wall across a pinning site, and implicitly the wall energy gradient, increases. Dislocation tangles are energetically significant enough to produce effective pinning sites for domain walls [8,9]. Dislocation density increases during plastic deformation lead to changes in the domain wall energy gradient at pinning sites.…”

“…Reversible magnetic permeability is the limited value of the incremental permeability when the incremental permeability is at ∆H→0 [9]. Magnetic properties are usually measured at the fixed magnetic field applied to the test samples in most magnetic techniques.…”