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M: Metallphysik

M 18: Postersitzung

M 18.13: Poster

Dienstag, 9. März 2004, 14:30–16:30, Saal C

Evaluation of Carbon Diffusivities in Steels from Concentration-Distance Curves with Phase Transformation by Finite Element Analysis — •Jürgen Gegner — SKF GmbH, Material Physics, Ernst-Sachs-Str. 5, D-97424 Schweinfurt

Application of the isothermal Rhines pack decarburization technique for the determination of composition-dependent diffusion coefficients of carbon in the austenite phase of low-alloyed steels at common austenitising temperatures between 1070 and 1170 K results in an austenite-ferrite phase transformation in the edge zone of the sample caused by the carbon loss. This is shown by the concrete example of through-hardenable rolling bearing steel SAE 52100 (German denotation: 100Cr6) annealed at 1123 K for 5 h, where the decarburization profile is measured with high accuracy and spatial resolution by secondary ion mass spectrometry. Due to the phase transformation, a modified Matano analysis cannot be applied. Thus, a FE code is developed that permits data fitting by automatized profile simulation. This way, the carbon diffusivity in austenitic SAE 52100 is derived from the measuring curve. The obtained result is compared with literature data on binary Fe-C and ternary Fe-Cr-C.