Plasma-based ion implantation and electron-bombardment for large-scale surface modification of materials

In this paper, we present the use of plasma-based ion implantation (PBII) and plasma-based electron bombardment (PBEB) for large-scale surface modification of materials, which has been under development at Hughes Research Laboratories. In PBII, a part to be implanted is immersed in a gaseous-or metal-ion plasma and pulse biased to a high, negative potential (20-250 kV) to implant positively-charged ions omnidirectionally and simultaneously over the part surface. In PBEB, the polarity of the pulse-bias is reversed to bombard negatively-charged electrons omnidirectionally and simultaneously over the part to achieve surface or bulk heating. Both PBII and PBEB have been conducted at 100 kV, 100 kW levels in a 1.2 m diameter x 2.4 m long vacuum chamber to implant, surface and bulk harden, as well as surface alloy and braze objects. As examples, we show the use of PBII to achieve up to an 8x improved wear life of TiN-coated cutting tools subjected to multiple regrinds under actual gear-manufacturing wear conditions, as well as a >2.5x improved wear life of TiN-coated foundry blocks subjected to actual high-compression, sand-casting manufacturing wear conditions. We also show the use of the PBEB process to normalize, quench-harden and surface-heat pinion gears in a faster, more-efficient manner than achieved using conventional heat-treat techniques. (C) 1997 Elsevier Science S.A.