Abstract

The mechanical properties of Al₂O₃ have been improved by implantation of C and N ions at doses of 1 × 10¹⁵ to 1 × 10¹⁸ ion cm⁻². The hardness, fracture and scratch toughness of the implanted layers were examined. The increase in hardness was ca. 92% at 1 × 10¹⁷ N ions cm⁻², but only 6% at 1 × 10¹⁷ C ions cm⁻². The maximum fracture toughness was 95% greater than that of the unimplanted substrate at a fluence of 3 × 10¹⁷ N ions cm⁻², and ca. 25% greater for 5 × 10¹⁷ C ions cm⁻². The mechanisms of hardening and toughening by C and N ion implantation were investigated by XPS, electrical resistance and Raman spectroscopy measurements. The surface electric resistivity decreased to ca. 10⁷ Ω cm for N⁺ or C⁺ ion implantation. Nitrogen implantation produced Al, AlN or AlON while carbon implantation led to a carbon film, Al, Al₄C₃ or Al₄O₄C on Al₂O₃. The hardening and toughening on Al₂O₃ surface layers was attributed to chemical reactions, with the amount of modification depending on the C and N ion implantation dose.