Microstructure of TiC Layers on Iron and Carbon Steel Formed By Elevated-Temperature Ion Implantation

Abstract

In several previous investigations, it has been shown that the implantation of carbon-active elements such as Ti, Hf, Ta, and Nb into Fe or steel specimens can produce low-friction, wear-resistant surface layers, provided that the implanted element is chemically bound to a sufficient concentration of carbon. For the case of room-temperature implants, the source of the carbon can be either a directly implanted layer or carbon that is adsorbed from the residual atmosphere of the target chamber. For these room-temperature implants, the surface layers consist of an amorphous Fe-Ti-C alloy. In more recent work, it was observed that the implantation of 5 x 1017 Ti/cm2 at 190 keV into Fe or carbon steels at temperatures between 600 and 800°C produced a near-stoichiometric crystalline TiC layer, approximately 60 nm thick, which was continuously graded in composition into the substrate. For pure Fe, the source of the carbon was shown to be the residual atmosphere, while for steels containing greater than 0.1 wt.% C, the source was the C in the alloy.