Overview on applications of materials modifed by intense pulsed electron beams

Summary form only given. Surface modification of materials using intense pulsed electron beams result in an improvement of several properties like wear, corrosion and oxidation resistance. Three different treatment modes can be distinguished: rapid melting and solidification, surface alloying of coatings into the bulk and surface-fusing of coatings to the bulk. All three versions of surface treatment were performed using the GESA facilities having following parameters: accelerating voltage 80-400 kV; power-density 2-6 MW/cm²; beam-diameter 4-10 cm; pulse-duration 4-250 mus. Such pulses applied on material surfaces lead due to the rapid re-solidification to a change in microstructure and in the case of surface alloying also to a different chemical composition. The change in microstructure of 16MnCr5 steel after the GESA treatment increases the hardness by 60 to 80%. Gears of such material treated by GESA and tested under realistic conditions showed an increase of wear resistance by a factor of 6 to 8. Other applications are stationary gas turbine blades. There the thermal cycle stability of thermal barrier coatings deposited on HVOF sprayed MCrAlY coatings could be increased by a factor of two compared to none treated HVOF sprayed coatings. Here the reduced surface roughness in combination with an almost theoretical density of the treated layer is the major distinction of the GESA process in comparison to the non treated case. Beside rapid solidification surface alloying is an other subject of recent investigations. For example, surface alloying of Zr into MCrAlY reduces the growth rate of alumina scales under oxidizing atmosphere at 950degC. However the Zr content after treatment must below 1 wt% to minimize the brittle cracking of the surface layer after cooling down. Surface alloying of Al into various steels using an intense pulsed electron beam increase its oxidation resistance in liquid lead alloys by the selective formation of an alumina scale. More- - than 1000 h of exposure without significant scale growth was already observed. 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. The influence of surface fused coating on the mechanical properties is investigated performing low-cycle-fatigue tests and pressurized tubes. Both tests do not show any negative response of the surface modified layer onto the mechanical properties.