Non-destructive microstructure-sensitive characterization of wear progress in case-hardened 16MnCr5 gear wheels

Marina Knyazeva, TU Dortmund University, Dortmund, Germany
Frank Walther, TU Dortmund University, Dortmund, Germany
Fabian Pöhl, Ruhr University Bochum, Bochum, Germany
Leonard Gondecki, Ruhr University Bochum, Bochum, Germany
Monika Kipp, TU Dortmund University, Dortmund, Germany
Dirk Biermann, TU Dortmund University, Dortmund, Germany
Peter Tenberge, Ruhr University Bochum, Bochum, Germany

The evaluation of wear progress on gear wheels tooth flanks made of 16MnCr5 (1.7131) was performed using non-destructive micro-magnetic testing, specifically Barkhausen noise (BN) and incremental permeability (IP) measurements. Based on the physical interaction of microstructure with magnetic field, the micro-magnetic characterization allows analyzing all microstructural changes caused by wear, including phase transformation and development of residual stresses. Due to wide parameter variation and application of bandpass filter of micro-magnetic signal, it is possible to indicate and separate the main damage mechanisms considering the wear development under the surface. It could be shown that the maximum amplitude of Barkhausen noise correlates directly with the profile deviation and increases with the progress of wear. Surface investigations via optical and scanning electron microscopy indicated strong abrasion wear with micro-pittings and micro-cracks, visible in cross-section after 3E5 cycles. The result of abrasion of surface layer is the decrease of residual compression stresses, which was indicated by means of coercivity of BN analysis. The increase of surface roughness associated to wear, characterized via white light interferometer is reflected in maximum BN amplitude. Using complimentary microscopic characterization in cross-section, strong correlation between micro-magnetic parameter and microstructure was confirmed and wear progress was characterized in dependence of depth under the wear surface. The phase transformation according to wear development, measured by means of X-ray diffraction and electron backscattered diffraction (EBSD) was also detected by micro-magnetic testing.

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