| A new plasma source ion implantation device for inner and outer surface implantation of materials has been developed . Based on this device the experimental study of plasma diagnostics and sheath propagation dynamics were made by using Langmuir probe. By means of AES, XPS, XRD, SEM and TEM the inter-reaction between implanted ion and metal substrate during plasma source ion implantation, corresponding reactive phase and microstructure of implanted layer were investigated systematically The surface hardness and tribological properties of Ti6A14V, LY12, 40Cr and CrWMn alloys implanted with nitrogen ion were tested and the surface modification mechanism was analyzed.The plasma source ion implantation device consists of pulsed negative high voltage power, hot cathode arc discharge system, vacuum chamber and target stage, vacuum system and monitor system. The implanting energy is in the range of 10 100 keV,repetitive frequency 10 500 Hz, pulse width 2 50μs , plasma density up to 1× 10 cm-3. The increase of filament current and gas pressure can obviously raise the plasma density . Plasma electron temperature rises with the increase of filament current and remarkably decreases with the increase of gas pressure.A new plasma source ion implantation method and a corresponding plasma sheath model for inner surface implantation are presented first in this paper. Following this model a differential equation of sheath propagation is derived. The experimental measure of sheath propagation dynamics shows that this model is in good agreement with the experiment data and it can be used to describe the dynamic characteristics of sheath propagation during implantation for inner surface modification This new method has been successfully applied for inner surface modification of 40 Cr steel cylinder.Different nitride reactive phases were formed in the implanted layer of four metalmaterials which were implanted with nitrogen at room temperature. Reactive phase is fee TiN for Ti6A14V , hexagonal A1N for LY12 , Fe2N and CrN for 40Cr and CrWMn alloys. With the increase of the implantation dose the amount of the reactive phase increases. Heat treatment after implantation promotes the inter-reaction between implanted ions and substrate atoms so as to accelerate the formation and growth of reactive phases. It is noticeable that nitrogen ion implantation at room temperature induced the age precipitating process of LY12 alloy, and temper transformation of quenching structure caused by ion implantation was observed in the implanted layer of 40Cr and CrWMn alloys. Besides, the amorphous structure, dislocation network and sub-grain refinement caused by the irradiation damage during implantation were also discovered in the implanted layer.When implanted with 2.2 * 1017N+ cm'2, the surface hardness of all the four metalmaterials is significantly increased and further improved by the annealing treatment after implantation. But overannealing will lead to the substrate softening After implanted with 4.8 x 1017N+cm"2 the tribological properties of 40Cr and CrWMn alloys are obviously improved. Analysis results show that it is the implantation induced NT solid-solution, dislocation tangle and precipitation of nitride phases that cause the surface hardening of the implanted materials, which, in turn, lead to the improvement of tribological properties of the implanted materials.
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