James J. Leddy

Formation of a BN layer on the surface of B4C using nitrogen implantation

Abstract The surface of B 4 C was irradiated using nitrogen ions and then examined to determine the alterations in the surface chemical and mechanical properties following implantation. Pure boron was also implanted to compare uptakes and chemistry. The implantations were performed in situ at 10 keV in an ultrahigh vacuum system and at 100 keV using a commercial implanter. For doses up to 5.0 × 10 17 atoms cm -2 all implanted nitrogen reacted. The nitrogen implanted (10 keV) into either B 4 C or boron was chemically in the form of BN. 100 keV nitrogen implantation into boron resulted in BN formation while a boron carbide-nitride species was formed using B 4 C. Nitrogen doses of about 6.0 × 10 17 cm -2 at 100 keV for B 4 C produced chemical halos, 2 – 6 μm in diameter, around a crater owing to expulsion of a TiB 2 particulate impurity. The B 4 C surface, modified at 100 keV, (dose less than or equal to 5.5 × 10 17 cm -2 ) showed a 60% reduction in the pin wear scar diameter and a 200% increase in the coefficient of friction compared with the unimplanted surface. These changes in the surface chemical and mechanical properties suggest that a hard BN layer forms on B 4 C following nitrogen ion implantation.