Micro-Magnetic and Microstructural Characterization of Wear Progress on Case-Hardened 16MnCr5 Gear Wheels

Abstract

The evaluation of wear progress of gear tooth flanks made of 16MnCr5 was performed using non-destructive micro-magnetic testing, specifically Barkhausen noise (BN) and incremental permeability (IP). Based on the physical interaction of the microstructure with the magnetic field, the micro-magnetic characterization allowed the analysis of changes of microstructure caused by wear, including phase transformation and development of residual stresses. Due to wide parameter variation and application of bandpass filter frequencies of micro-magnetic signals, it was possible to indicate and separate the main damage mechanisms considering the wear development. It could be shown that the maximum amplitude of BN correlates directly with the profile form deviation and increases with the progress of wear. Surface investigations via optical and scanning electron microscopy indicated strong surface fatigue wear with micro-pitting and micro-cracks, evident in cross-section after 3 × 105 cycles. The result of fatigue on the surface layer was the decrease of residual compression stresses, which was indicated by means of coercivity by BN-analysis. The different topographies of the surfaces, characterized via confocal white light microscopy, were also reflected in maximum BN-amplitude. Using complementary microscopic characterization in the cross-section, a strong correlation between micro-magnetic parameters and microstructure was confirmed and wear progress was characterized in dependence of depth under the wear surface. The phase transformation of retained austenite into martensite according to wear development, measured by means of X-ray diffraction (XRD) and electron backscatter diffraction (EBSD) was also detected by micro-magnetic testing by IP-analysis.

Barkhausen Noise Emission in Hard-Milled Surfaces

“…Magnetic Barkhausen noise (MBN) is a promising non-destructive technique that could be potentially adapted for fast and reliable surface monitoring. An increasing number of studies can now be found in which MBN is investigated as a function stress state [ 1 , 2 , 3 , 4 ], dislocation density [ 5 , 6 ], carbides or nitrides size and distribution [ 7 , 8 ], presence of non-ferromagnetic phases [ 9 ], etc. However, this technique is most widely employed for monitoring ground surfaces in real industrial applications.…”

Assessment of Tendon Prestressing after Long-Term Service via the Barkhausen Noise Technique

“…Domain walls are pinned by dislocation tangles, precipitates, grain boundaries, non-ferromagnetic particles, or phases, etc. [18,19,20,21]. On the other hand, the stress state strongly affects the domain walls’ alignment.…”

A time series classification approach to non-destructive hardness testing using magnetic Barkhausen noise emission

“…In the experimental setup of this contribution the MBN measurements were performed with an excitation frequency of f M = 300 Hz with an amplitude of U = 0.573 V. The research question whether this configuration leads to an optimal correlation between the resulting MBN signal of this specific material and the hardness of the material is, albeit important for future research, out of the scope of this contribution. The depth of the MBN analysis is especially dependent on the used excitation frequency due to the skin effect [24]. Thus, higher excitation frequencies lead to analysis closer to the material surface.…”