| The MPPMS is a high-performance coating deposition technology which was developed from the HIPIMS technology.The researchers improved the pulse shape of the HIPIMS technology.The most important feature of the MPPMS pulse shape is that the pulse shape could be arbitrarily tailored into multisteps which contain the weak ionization pulse segment,the strong ionization pulse segment and the transition phase from low power discharge to high power discharge.Together with thses multisteps,the higher deposition rate and stable deposition processes could be achieved.In this paper,the AlCrN and Quaternary AlCrTiN hard coatings were designed and deposited by MPPMS/DCMS co-sputtering system with different discharge voltage and Ti target power.Detailed studies have been conducted to investigate the influence of these parameters content on the microstructure,mechanical properties and tribological behaviors of the AlCrN based composite coatings.The MPPMS technology could produce the large ion beams without defects such as metal droplets.By applying bias voltage,the high ionization particle beams could deposit on the surface of substrate in a relatively higher energy,as a result,the atoms attaching to the coating loosely would be stripped down,the roughness and density of the coatings could be significantly improved.All the coatings deposited by MPPMS/DCMS co-sputtering were very dense and smooth,the larger particles,metal droplet,micro cracks and pinhole defects were not found,indicating a good compactness of the coatings.The AlCrN based coatings showed a typical B1-NaCl structure,involving?111?,?200?,?220?and?311?four peak diffraction at different discharge voltage and Ti target power.The discharge voltage influenced the ionization of target material and the energy of particle beam reaching the coating forming surface,thereby affecting the microstructure and contents of the coatings significantly.And the power of Ti target affected the phase structure and element composite of the coatings through influencing the content and energy of each element in the depositing particle beam.As increasing the power of Ti target,h-AlN diffraction peak weakened gradually,and then disappeared,which meant that doping Ti element into AlCrN coatings could inhbit the formation of h-AlN phase effectively.As for the mechanical properties,with the increase of the discharge voltage,the hardness of the AlCrN coatings initially increased from 24.4 GPa at 350 V to maximum values of approximately 30.8 GPa at a charge voltage of 450 V.When the discharge voltage was 540V,as the increase of Ti target power,the hardness of AlCrTiN coatings increased firstly and then decreased,the hardness reached the maximum value of 28.3GPa.In the thermal stability performance,the mechanical properties decreased with the increase of vacuum annealing temperature duing to the phase transition in high temperature,grain growth and the disappearation of residual stress.After vacuum annealing 1hour in 1000?,the hardness of all the coatings deposited at different discharge voltage and Ti target power decreased to 16 GPa.As for the tribological properties of coatings deposited at different discharge voltage and Ti target power,the discharge voltage had great influence to the wear resistance of AlCrN nano-composite coatings in high temperature.When the temperature was 600?,the coating deposited at 400V reached the minimum wear rate value,7.7×10-15m3/N·m,as the temperature increased to 800?,the coating deposited at400V also has the minimum wear rate value,11.2×10-15m3/N·m.Ti target power affected the composition,mechanical properties and thermal stability of the coatings,so it had great influence on the tribological properties.For the tribological properties at room temperature,with the increase of Ti target power,the difference of the average coefficient of friction between the coatings could be ignored,but the wear rate of the coatings showed the tendency of decreasing firstly and then increasing,the minimum wear rate value was 1.7×10-17m3/N·m.In high temperature tribological properties,the average coefficient of friction decreased as increasing the temperatue of the friction test.The wear rate of coatings with different Ti content had a trend of increasing after reaching the minimum.When the temperature was 600?,the coating deposited at 3.0kW reached the minimum wear rate value,6.9×10-15m3/N·m,as the temperature increased to 800?,the coating deposited at 3.0 kW had the minimum wear rate value,14.2×10-15m3/N·m.And the coatings cutting experiments showed that the AlCrTiN coatingsl could improve the performance of the tools remarkably.At different cutting speeds,the lifetime of Al CrTiN coated milling cutters was about 4-9 times than that of uncoated milling cutters.The cutting force increased with the increasing of cutting distance,and the AlCrTiN-coated milling cutter increased relatively slowly compared with the uncoated milling cutter,and the cutting force decreased with the increase of cutting speed and the cutting force was the least when the cutting speed was 300m/min,under different cutting speed?100-300m/min?.In addition,compared with the Multi-arc ion Plating AlCrTi N coatings,the coatings deposited by the MPPMS/DCMS co-sputtering technology have the more excellent tool life and the cutting properties. |
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