Steel components were carburized in an industrial facility. Measurements with four independent electromagnetic test methods
were made at the components in order to test the depth of the carburized layer (case depth). The four methods have different
penetration depth and sensitivity to material properties. Models to predict the case depth were built based on multiple
regression methods. It could be shown that the testing accuracy could be significantly improved by using a combination of
test methods. The reason was that a thin, decarburized layer prevented the accurate measurement by a single method. The distorting
effect of the decarburized layer could be corrected by combining a method with deep penetration depth with a method
that has only a shallow penetration depth.
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