The use of magnetic Barkhausen Noise Analysis (BNA) has been proven to be an effective tool for the
non–destructive detection of microstructural anomalies in ferrous materials. Used as an in–process tool for
the detection of surface temper burn, heat treat defects and stresses, BNA is a quick comparative and
quantitative alternative to traditional destructive methods.
Applications of BNA as a quality control tool in gear production have existed for nearly two decades. This
paper presents examples that demonstrate how BNA is used to evaluate changes in microstructural
properties. Quantitative results correlate BNA test values to X–Ray diffraction values for the detection of
changes in surface residual stress. Other quantitative analysis correlates BNA test values to surface
hardness values for the detection ofre–tempering burn. Qualitative results correlate BNAtest values to acid
etch patterns/colors for the detection of re–tempering burn defects.

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