Non-Destructive Characterization of Subsurface Plastic Deformation in Case Carburized Steel Using Magnetic Barkhausen Noise Technique

Brian Andrew Shaw,Mohamed Ali Ballem,Mohamed M Blaow

doi:10.24018/ejers.2019.4.12.1691

Brian Andrew Shaw, Mohamed Ali Ballem + Show 1 more

Open Access

https://doi.org/10.24018/ejers.2019.4.12.1691

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Abstract

The effect of extreme loading in bending was investigated by magnetic Barkhausen Noise (MBN) and X-ray diffraction (XRD) in two types of inhomogeneous steels that widely used in gear industry. EN 36 and H8620 steels in the carburized, tempered and ground condition were investigated after unloading from high stress levels. The inhomogeneity arising from the variation in carbon content showed up clearly by double peaks MBN profiles before loading. The first MBN peak at low field revealed the soft subsurface region and the second peak at higher field revealed the hard surface layer. Residual stresses profiles were produced by XRD before and after loading to probe plasticity in the cross sections of both specimens. Barkhausen noise measurements showed a considerable change in the first peak height in both steels as a response to plastic deformation in tension and compression in the subsurface material. The height of the second peak remained unchanged in EN 36 specimen but increased slightly in the H8620 specimen. The residual stress measurements after unloading indicated that the subsurface materials after a depth of 0.4 mm in both specimens were yielded. The surface layer of the H8620 steel was also affected slightly by bending as revealed by an increase in the second MBN peak height and confirmed by XRD as indication of yielding. The experiment confirmed that the magnetic Barkhausen noise can be used to characterize yielding in inhomogeneous steels non-destructively.

Highlights

Steel components are often subjected to hardening processes in which the surface is hardened in order to improve its wear and fatigue resistance, these processes introduce a case-hardened layer; the hardness of this layer is higher than that of the bulk material, and its depth is varying depending on the different requirements and applications
The aim of this paper is to examine the applicability of magnetic Barkhause noise technique to evaluate the residual stresses at the subsurface region, and to explore the possibility of detecting plastic deformation nondestructively across the section of case carburized steels
Examples of the resulted type of magnetic Barkhausen Noise (MBN) profiles are shown in Fig. 4 for one magnetization cycle for both steels before loading

Summary

Introduction

Steel components are often subjected to hardening processes in which the surface is hardened in order to improve its wear and fatigue resistance, these processes introduce a case-hardened layer; the hardness of this layer is higher than that of the bulk material, and its depth is varying depending on the different requirements and applications. Case hardening process is often used for the manufacture of machine parts such as gears that need to have externally hard surface to endure wear and tear, but soft internally to withstand shock. During the manufacturing process of case-hardened steel gears, residual stresses are developed [1], [2]. Blaow is with Industrial Engineering Department, Faculty of Engineering, Misurata

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