Friction and wear of nitrogen-implanted glassy carbon

Abstract

Scratch friction and wear behavior of a glassy carbon (GC) implanted with a high dose of nitrogen as studied when in contact with a steel ball and with diamond indenter. A sliding velocity of V = 0.2 mm s −1 and loads from 0.5 to 4 N during 50–300 cycles were applied in laboratory air (humidity ~50%). Smoother and more closely compacted surfaces than in the virgin state were obtained at doses of 1 × 10 16–1 × 10 17 ions cm −2, but surfaces became heavily blistered at higher ion dose levels (1–1.5 × 10 18 ions cm −2). It was shown that the enhancement of wear resistance is associated with the amorphization of the implanted layer, which leads to a rise in strength of implanted GC and to a decrease in the rate of crack propagation in a hostile environment. Crescent-shaped cracks were observed on the surface of virgin GC subjected to friction with a steel ball. At higher doses of implantation, steel wear particles adhered to the rough blistered surface in contact with the steel ball, and bubbles burst following contact with the diamond indenter. The implant dosage needed for maximum wear resistance was found to be in the vicinity of 1 × 10 16 ions cm −2. The influence of the gradual change in the bonding mode with the of implantation dosage (from sp 2, characteristic for graphite and GC, to sp 3, characteristic for diamond) on the tribological properties of the carbon materials is discussed. The synergetic influence of implantation and environmental humidity was adduced to explain the observed behavior of GC in friction and wear.