PULSED ELECTRON BEAMS AND THEIR USE FOR MATERIAL
MODIFICATION
A. Weisenburger1,
V. Engelko2, W. An1, Annette Heinzel1, Adrian
Jianu1, Fabian Lang1, G. Müller1 and
Frank Zimmerman1
1 Forschungszentrum Karlsruhe, Institut für
Hochleistungsimpuls- und Mikrowellentechnik,
Hermann-von Helmholtz Platz 1
76344 Eggenstein-Leopoldshafen, Germany
2 Efremov Institute of Electrophysical
Apparatus, 189631,
ABSTRACT
Intense pulsed electron beams are applied for surface
modification of materials since several years in our laboratories. The intense
pulsed electron beams are generated by the GESA (Gepulste
Elektronen Strahl Anlage) facilities[1]. One
peculiarity of these facilities are the multi point
explosive emission cathodes allowing the generation of large area intense
electron beams. These beams have following parameters: accelerating voltage between
80–400kV, power-density at the target from 2 to 6MW/cm2,
beam-diameter 4 to 10cm and pulse-duration of 4 to 250µs. Electron beams
deposit their energy volumetric in the target and therefore an almost adiabatic
melting of a definite surface layers is achieved. The underlaying
bulk remains relatively cool during the pulse and therefore rapid cooling <
107K/s by heat conduction into the bulk will take place. This
results in a change in microstructure and in the case of surface alloying also
to a change in chemical composition [2]. An improvement of properties like
wear, corrosion and oxidation resistance was found.
Changes in microstructure of 16MnCr5 steel after the
GESA treatment increases the hardness by 60 to 80%. GESA treated gears of this material
showed an increase in wear resistance by a factor of 6 to 8. The thermal cycle
stability of thermal barrier coatings deposited on HVOF sprayed MCrAlY coatings
of stationary gas turbines blades could be increased by a factor of two
compared to none treated HVOF sprayed coatings [3]. GESA treatment of Ti -
blades lead to increased fatigue strength of about 40% compared to untreated
blades [4]. Surface alloying of Al into steels increases their oxidation
resistance in liquid lead alloys by the selective formation of alumina scales.
More than 10000h of exposure without significant oxidation and corrosion are
performed. Surface-fusing of FeCrAlY coatings is investigated as a corrosion
protection layer in liquid lead alloys too. Such layers show the same positive
oxidation behaviour like the Al- surface alloyed materials without
deteriorating the mechanical properties of the materials as shown in
low-cycle-fatigue tests [6] and with pressurized tube tests [7].
Oral
References
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