Magneto-Acoustic Emission and Magnetic Barkhausen Emission for Case Depth Measurement in En36 Gear Steel

• Published in: IEEE transactions on magnetics Vol. 45; no. 1; pp. 177 - 183
• Main Authors: Wilson, J.W., Gui Yun Tian, Moorthy, V., Shaw, B.A.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.01.2009; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Applied sciences; Case depth; Case hardenability; Case hardening; Cross-disciplinary physics: materials science; rheology; Emission; En36 steel; Energy measurement; Exact sciences and technology; Gears; Heat treatment; Industrial economics; magnetic Barkhausen emission; Magnetic domain walls; Magnetic domains; Magnetism; magneto-acoustic emission; Manufacturing industries; Materials science; Metals industry; Metals. Metallurgy; Molecular beam epitaxy; Motion measurement; nondestructive evaluation; Other topics in materials science; Peening; Physics; Production techniques; Steel; Structural steels; Surface treatment; tempering; Thermochemical treatment and diffusion treatment; Thermochemical treatment; magnetic Barkhausen emission; magneto-acoustic emission; Nondestructive testing; Barkhausen effect; Heat treatments; Hardening; En36 steel; Gears; case hardening; Tempering; Acoustic emission; nondestructive evaluation; Carburizing; Case depth; Magnetic properties
• ISSN: 0018-9464; 1941-0069
• DOI: 10.1109/TMAG.2008.2007537

There is a need in industry to supply safe, economical, and reliable techniques to characterize surface treatments such as case hardening and peening of steel components and structures, both at the manufacturing stage and in service. Magnetic Barkhausen emission (MBE) has proved successful for these tasks, but has severe limitations in terms of measurement depth of the technique and deeper treatments such as laser peening and case hardening often fall outside the scope of MBE inspection. The domain wall motion that generates MBE also causes a release of elastic energy known as magneto-acoustic emission (MAE), which has a much greater measurement depth, and so offers a complementary technique to extend the measurement depth for the characterization of surface treatments in steel. In this paper, comparative MBE and MAE results from case hardened En36 gear steels are presented in the form of signal profiles and correlations are drawn between MBE and MAE profile features and domain activity within the soft core and the case hardened layer. The results show that the overall amplitudes for both MBE and MAE exhibit a good correlation with case depth, but profile analysis for MAE is ambiguous, so possible interpretations of the MAE profile are discussed.