Discharge Of Graphite Cathodic Arc With High Pulse Current And Structure And Properties Of Ta-C Thin Films

The ta-C coating has many excellent properties,combining the advantages of graphite and diamond,such as good wear resistance,high hardness,good chemical stability and good biocompatibility,thus has a wide range of applications.The mismatched microstructure between the ta-C and the HSS gave rise to the accumulation of the internal stress,which would degraded the adhesion,And the film has a low deposition rate with high resistivity.In order to improve the adhesion of the film,the Cr/CrC transition layers was designed.To increase the ionization of materials from the target as well as the deposition rate,the high pulse power supply made by the research group was used?with the peak current of 1000A?.The discharge characteristics and OES of the graphite target are studied by adjusting the pulse frequency,pulse width,gas pressure and nitrogen flow rate.The ta-C films were prepared with different bias voltages,pressures and peak current.The ta-C films with N can reduce internal stress,improve adhesion,and increase corrosion resistance.The ta-C:N films were prepared with different nitrogen flow rates.The structure and properties of the films were studied.The discharge and OES studies have shown,with pure argon conditions,when the pulse width is constant,As the frequency increasing,the peak current decreases and the substrate bias current decreases,and the ratio of C?1+?/Ar?1+?keeps decreasing;when the frequency is constant,the peak current decreases as well as the substrate bias current,and C?1+?/Ar?1+?decreases first and then increases.With the increase of pressure,the bias current of the substrate gradually decreases,and C?1+?/Ar?1+?decreases continuously.Under the condition of nitrogen-argon mixed gas,the bias current of the substrate increase with the increase of peak current,C?1+?and N₂?1+?also increases,High peak current can significantly increase the ionization rate of graphite and nitrogen,and the target is not easily poisoned.As the nitrogen flow rate increases,C?1+?decreases,N₂?1+?increases,and the matrix bias current decreases.The analysis of structure and properties of the films show that the ta-C film had the smallest number of particles and the cleanest surface at a bias voltage of-80 V.The surface number of particles gradually decreased with the increase of gas pressure.With the increase of peak current,the deposition rate increases first and then decreases.When the peak current is 600A,the deposition rate is the fastest,reaching 7.2nm/min.As the nitrogen flow rate increases,the number of large particles on the ta-C:N surface decreases.The deposition rate of ta-C increases with the increase of bias voltage and decreases with the increase of gas pressure.The deposition rate of ta-C:N decreases with the increase of nitrogen flow rate.With the increase of bias voltage,the content of sp³ bond in ta-C film increased first and then decreased,and it was the highest at-80V.With the increase of gas pressure,the content of sp³ bond in ta-C film decreased gradually.The content of sp³ bond increases first and then decreases with the increase of pulse current,and is the largest at 600A.With the increase of nitrogen flow rate,The nitrogen content of the prepared ta-C film gradually increased,and the content of sp³ bond gradually decreased.The change in hardness of the prepared film was consistent with the change in sp³ content,the hardness reached a maximum of 49.2 GPa when it is0.03Pa,The hardness of the film after nitrogen doping is significantly reduced,and as the nitrogen content increases,the hardness gradually decreases.The corrosion resistance test shows that the corrosion resistance of ta-C is better than that of the substrate,and the corrosion resistance of the film is greatly improved after nitrogen doping.