Characterization of drills implanted with nitrogen plasma immersion ion implantation

Plasma immersion ion implantation (PIII) is a method which retains the advantages of conventional beam line implantation while circumventing the limitations like beam-rastering and target handling for large objects with a complex geometry. However, an electric field which is too high, especially at small tips or sharp edges, induces arcing, which subsequently damage the implanted workpieces. Here we present investigations performed on high-speed steel drills with a diameter of 0.47 mm and 8 mm, as well as flat samples, implanted with nitrogen-PIII at different voltages between 5 and 25 kV at an elevated temperature of 400 degrees C. For the 0.47 mm drills damage from arcing and subsequent decrease of the tool cutting life is correlated with the implantation voltage. For the 8 mm drills no detrimental effect of arcing was observed and a lifetime increase by 100% was found. The mechanism leading to this increase is the formation of a very hard compound layer of iron nitrides followed by a diffusion layer of some 25 I-lm as determined on the flat samples with hardness, GDOS, and XRD measurements. Further annealing of the samples reduced the surface stress while retaining the high hardness. (C) 1998 Elsevier Science S.A.