Titanium carbonitride [Ti(CN)] films were deposited on the surface of No. 45 steel for modification using the high power density pulsed plasma technique. The pulsed plasma is generated from a coaxial plasma gun and has a high electron temperature of 105-106 K and a high electron density of 10(14)-10(16) cm(-3); high translation titanium carbonitride [Ti(CN)] films were deposited at 30-50 km/s and were only 60 mu s wide. The substrates were maintained at room temperature during the film deposition, but a stronger adhesion of film to substrate existed. A wide mixing interface between the Ti(CN) films and the substrate formed and resulted in a high adherency of the films to the substrate. The surface microhardness of No. 45 steel increased remarkably due to the formation of titanium carbonitride films.