Correlation of Magnetic Barkhausen Emission Profile with Strength of Thermally Degraded 2.25Chromium–1Molybdenum Steel

Abstract

A non-destructive magnetic Barkhausen emission (MBE) technique was applied to assess thermal degradation of 2.25Cr-1Mo steel, exposed to 630 C for up to 4800 h. The peak position and the peak amplitude in MBE profile decreased and increased, respectively, as a linear function of cube root of isothermal degradation time. These changes in MBE profile were related to the carbides coarsening during thermal exposure. An empirical correlation between the ultimate tensile strength (UTS) and the peak position in the MBE profile was also obtained by a linear regression analysis.

Magnetic evaluation of accelerated aging degradation on 2.25Cr-1Mo steel with martensitic and bainitic microstructure

“…Hence, a large magnetizing force is required to remove the residual field, resulting in a higher coercive force. A decrease in pinning density in terms of microstructural degradation such as grain growth (which reduces grain boundary area), lath broadening (which reduces lath boundary area), spheroidization (which reduces the surface area of the carbides), coarsening of precipitates in the expenses of a large number of finer precipitates (which decreases the number density of precipitates), and relaxation of compressive residual stress (which reduces the strain field) decreases the coercive force in ferromagnetic materials such as steels (10)(11)(12)(13)(14)(15)(16)(17)(18).…”

“…The development of suitable NDE techniques for monitoring the health of the components for precise evaluation of microstructure and mechanical properties is highly desirable. Magneticbased NDE techniques are in growing demand for the common pinning sites for the magnetic domain wall motion and dislocation motion in steels (9)(10)(11)(12)(13)(14)(15)(16)(17)(18). However, the sensitivity of the different magnetic parameters to various micro-constituents makes the technique complex to evaluate.…”

Microstructural characterisation of thermally degraded 2·25Cr–1Mo steel using ultrasonic measurement and its correlation with mechanical properties

“…2b-e which results in loss of coherency with the matrix leading to decrease in strength parameters of this steel. [30][31][32] The decrease in strength parameters including that of hardness (Figs. [3][4][5][6], therefore, could be attributed to the increased tendency towards carbide precipitation and precipitate coarsening (300 nm to y1500 nm).…”

Συσχέτιση Μαγνητικών Και Μηχανικών Ιδιοτήτων Με Μικροδομή Σε Συγκολλήσεις Φερρομαγνητικών Χαλύβων

“…Ομοίως, οι Blown [33] και οι Batista et al [10] διαπίστωσαν, ξεχωριστά ο καθένας, την πτώση της μαγνητικής απόκρισης με την αύξηση του ποσοστού σφαιροποίησης του σεμεντίτη εντός της φερριτικής μήτρας σε σιδηρομαγνητικά δείγματα χάλυβα. Οι Byeon et al [129,172] προσπάθησαν να συσχετίσουν το πλήθος των καρβιδίων που σχηματίζονται σε Cr-Mo χάλυβες, που έχουν υποστεί γήρανση, με την ενεργό τιμή του θορύβου Barkhausen. Διαπίστωσαν ότι καθώς ο αριθμός των καρβιδίων μειώνονταν με την αύξηση του μεγέθους τους, η μαγνητική απόκριση αυξάνονταν εξαιτίας της αύξησης της ταχύτητας μετακίνησης των τα μαγνητικών τοιχωμάτων.…”