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Electron Beam Hardening of Nanobainitic Steels

Piotr Śliwiński, Marek St. Węglowski, Janusz Pikuła, Tomasz Tański, Andrzej N. Wieczorek, Emilia Skołek

Because of the unique combination of their properties, nanobainitic steels containing Si are particularly attractive materials for use in gear manufacturing. However, in order to achieve desired results, it is first necessary to obtain a surface of sufficient hardness (i.e. to increase the hardness of the surface layer using surface hardening techniques). One of such techniques is electron beam hardening. Due to the high power of electron beam welding machines and properties of the electron beam itself, the above-named technology makes it possible to harden workpieces within a wide range of thicknesses. Research-related tests discussed in the article involved the hardening of blocks made of nanobainitic steel (30 mm × 150 mm × 20 mm) using the oscillation-deflected electron beam. Test specimens were subjected to surface hardening with the electron beam using different beam settings. Surface hardening techniques involved both moving the specimen relative to the heat source and quenching only with beam oscillation. As part of the study, finite element simulations were performed along with the validation of results. The test specimens were then subjected to Vickers hardness tests as well as to light microscopic and microstructural tests (using scanning electron microscopy).  The test results revealed that the electron beam hardening method made it possible to obtain hardened layers having a thicknesses of up to 1.9 mm. The distribution of hardness in the hardened zone was uniform, whereas the specimens hardened without movement were characterized by a higher average hardness of 674 HV0.1. The average hardness value of the hardened layer amounted to 626 HV0.1 in terms of the sample hardened at a speed of 250 mm/min. The results of the FEM numerical calculations were consistent with the results of the actual measurements, indicating that the assumptions and boundary conditions in the FEM modelling of the electron beam quenching process were defined correctly.

DOI: 10.17729/ebis.2023.2/3

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