Magnetic Barkhausen Noise in Quenched Carburized Nickel-Steels

Relation Between Magnetic Barkhausen Noise and Hardness for Jominy Quench Tests in SAE 4140 and 6150 Steels

“…For low carbon steels, which are magnetostrictive positive, macro compressive stress (of 1st kind) results in reduction of the MBN, whereas macro tensile stress (of 1st kind) increases the MBN signal [13,19]. In many cases, the dominant stresses are the micro-residual stress (of the 3rd kind), as previously discussed [8,18].…”

“…Also, magnetic measurements were effectively used by Kaplan et al [31] for studying microstructural changes in quenched AISI 8620 steel specimens. Summarizing, there is a clear trend indicating that when martensite volume fraction increases the MBN emission decreases, which should be attributed to occurrence of domain rotation in the martensite [8,32]. The aim of the present study is to characterize steel microstructures by evaluating, through the Barkhausen method, a continuous microstructure profile change, produced in a single sample by the Jominy end-quench test.…”

“…These defects may stop the movement of either dislocations or domain walls. The martensite transformation leads to (i) a large number of interfaces, (ii) carbon in solid solution generating stress in the lattice, (iii) a high density of dislocations [8].…”

“…In general, when the steel microstructure is finer, the harder is the material, because the interfaces act as obstacles for dislocations. If the grain size is very small, in the nanocrystalline size, another mechanism for magnetization reversal can happen: domain rotation [8]. The Barkhausen noise emission is smaller for domain rotation rather than for domain wall movement [10].…”

“…There are two main types of residual stress, macro-residual stress and micro-residual stress (also called of the first kind and of the third kind residual stress, respectively) [16][17][18]. The large XRD peak broadening after martensitic transformation suggests significant microresidual stress, caused by the high density of dislocations and carbon in solid solution [8]. The magnitude of macroresidual stress and micro-residual stress in cold-rolled low carbon steels were compared and it was found that the cold rolling process introduces significant micro residual stress (of the 3rd kind) [18].…”