The hardening process determines the quality of roller bearings in a crucial way. Therefore this process should be supervised using NDT methods. Eddy- Current Testing (ET) is in general well suited for checking structural changes in hardened steels. However the structure- property-relationships which ET bases on must be taken into account in order to apply these methods in a reliable way. Therefore dependencies between magnetic permeability μ, and electric resistance p and hardening temperature and annealing temperature, respectively were investigated for steel grade 100Cr6. Furthermore relationships between μ and ρ on the one hand and on the other hand carbon content solved on martensite and volume fraction of retained austenite, respectively had been found. Basing on these relationships conclusions were drawn to the applicability of ET regarding supervision of the hardening process of roller bearing steels.
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