Study Of Pulse Cathodic Arc Discharge Of Graphite And Deposition Of Ta-C Coatings

The ta-C coating has many outstanding properties.Its ultra-high hardness and chemical stability have produced enormous economic benefits in precision processing and automotive industries.Because of the large mechanical properties difference between ta-C coating and high speed steel,and the coating has large intrinsic internal stress,the coating has poor film adhesion properties.The ionization rate of carbon in the process of ta-C coating prepared by PVD is low,resulting in low deposition rate and poor performance of ta-C coating.In order to improve the adhesion properties of ta-C coating,the supporting layer structure was designed.In order to improve the deposition rate and performance of the coating,the ionization rate of plasma in the deposition process was improved by using pulse arc technology.In this paper,the home-made pulsed power supply was used to study the discharge characteristics and spectral characteristics of graphite pulsed cathode arc by adjusting the parameters such as pulse frequency,pulse width,average pulse current,pulse peak current,and pressure.A Cr/ ta-C was designed and ta-C coating was prepared on M2 high-speed steel and single-crystal Si wafers by pulsed cathode arc technology.By changing the deposition process,the effects of pulse peak current,deposition time,different rotation mode on the deposition rate,the particles,the adhesion strength,the coating structure and the nano-hardness were studied.The discharge test results show that when the average pulse current,the average DC current and the pulse width remains unchanged.With the increase of the frequency,the substrate current decreases,the value of C+/Ar+ decreases.When the average pulse current,the average DC current and pulse frequency remains unchanged,with the increase of pulse width,the substrate current decreases,C+/Ar+ value decreases first and then increases.When the average pulse current,the average DC current and the peak current remains unchanged,with the increase of the pulse width,the substrate current has not changed much,the C+/Ar+ value increases.When the average output current,the pulse width and frequency remains unchanged,with average pulse current increases,the substrate current increases and C+/Ar+ increases.When the average output current,the pulse width and pulse peak current constant,with the increase of the average pulse current,the substrate increases and the value of C+/Ar+ increases.All series of experiments,the substrate current decreased as the pressure increased,and C+/Ar+ decreased with the pressure increased.The analysis of the structure and properties of the ta-C coating shows that the adhesion strength of the coating becomes worse with the increase of deposition time,and the adhesion strength of the coating can be greatly increased by designing the interlayers.The coating thickness increases first and then decreases with the increase of the pulse peak current and reaches a maximum at 200 A.The sp3 bond content and hardness of the coating increased first and then decreased with the increase of the peak current and reached a maximum value of 57 GPa at 300 A.The thickness of the coating prepared in different rotate modes is 1:1.16:1.54,and the maximum sp3 content and maximum hardness values were obtained for the two-rotation process.