PULSED ELECTRON-BEAM TECHNOLOGY FOR SURFACE MODIFICATION OF METALLIC MATERIALS

This article concerns the foundations of a new technology for surface modification of metallic materials based on the use of original source s of low-energy, high-current electron beams. The sources contain an e lectron gun with an explosive-emission cathode and a plasma anode, pla ced in a guide magnetic field. The acceleration gap and the transporta tion channel are prefilled with plasma with the use of spark plasma so urces or a low-pressure reflected discharge. The electron-beam sources produce electron beams with the parameters as follows: electron energ y 10-40 keV; pulse duration 0.5-5 mu s; energy density 0.5-40 J/cm(2), and beam cross-section area 10-50 cm(2). They are simple and reliable in operation. Investigations performed with a variety of construction al and tool materials (steels, aluminum and titanium alloys, hard allo ys) have shown that the most pronounced changes of the structure-phase state occur in the near-surface layers quenched from the liquid state , where the crystallization front velocity reaches its maximum. In the se layers partial or complete dissolving of second phases and formatio n of oversaturated solid solutions and ordered nanosized structures ma y take place. This makes it possible to improve substantially the elec trochemical and strength properties of the surface layers. It has been established that the deformation processes occurring in the near-surf ace layers have the result that the thickness of the modified layer wi th improved strength properties is significantly greater than that of the heat-affected zone. Some examples of the use of low-energy, high-c urrent electron beams for improving the performance of materials and a rticles are given. (C) 1998 American Vacuum Society. [S0734-2101(98)03 604-5].