Analysis of structure and hardness between electron beam hardened areas

Matlák Jiří - VUT Brno (Czech Republic)

Straight energy application by electron beam belongs to the modern and efficient tools for surface heating. Thanks to focusing of high energy source to tiny spot arises high planar energy density, which is possible to use for welding, machining, engraving, surface heat and chemical-heat treatment, etc. From the point of view of nowadays machinery praxis this is a technique which allows extremely precise localization and dosage of applied energy to the specified part of surface. Then the exactly bordered area or the profiled detail can be treated with minimum energy surplus and thus minimal heat affected zone, distortions etc.

The device can work in several modes according to type of heating localization. First possibility is one-time planar heating, when the part doesn’t move (flash heating, flash hardening, flash welding). Size of concurrently (quasi-continuous) heated area is given by power of device, speed of beam scanning and possibility of modulating beam power, when created heated area should be maximal homogenous. Other possibility is gradual process, when electron beam heats defined area and the part is moving, eventually on the stable part is heated field moving thanks to beam deflection. This mode provides highest surface energy density. Hardened line could be only one or more lines are putted next to each other eventually with small overlap thanks to is possible to treat large areas. But these processes require structure analysis and properties of transitional areal between lines.

This contribution deals with finding maximal depth of hardened area by gradual hardening using device with 15 kW power and accelerating voltage 150 kV and describing transitional planar between individual surface hardened lines. Moreover are determined optimal parameters of hardening process.

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