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

Abstract

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 pulsebias 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 × 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 8 × improved wear life of TiN-coated cutting tools subjected to multiple regrinds under actual gear-manufacturing wear conditions, as well as a >2.5 × 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, quenchharden and surface-heat pinion gears in a faster, more-efficient manner than achieved using conventional heat-treat techniques.