Study On Preparation And Tribological Properties Of MoN-based Coatings Deposited By High Power Pulsed Magnetron Sputtering

Extending the working life of mechanical moving parts is the key to enhance its operational reliability.With the continuous development of industry in recent years,the materials of moving parts are facing more demanding service conditions of high speed,high and low temperature,high wear and high corrosion,thus putting higher requirements on the overall performance of the materials.Single material properties can no longer meet the requirements,by depositing one or more layers of metallic or non-metallic coatings on the surface of the substrate to effectively improve the substrate material resistance to high temperature stability,mechanical wear resistance,corrosion resistance and fatigue resistance is a good choice.MoN coatings are characterized by high hardness,excellent wear resistance and good chemical stability,and have good tribological properties in a wide temperature range,making them a good choice for surface protection coatings.The coating deposited through high power impulsed magnetron sputtering technology has a denser structure,flatter surface and fewer defects,better uniformity of the coating deposited on the substrate,and high utilization of the target material.Based on this paper,MoN coatings were deposited through high power impulsed magnetron sputtering technique,and the effects of nitrogen flow rate,bias voltage and peak current on the organizational structure,mechanical and tribological properties of the coatings were systematically investigated.Subsequently,Mo Si N composite coatings were prepared by doping with Si elements to further improve the overall performance of the coatings.Aiming at their use as surface protective coatings to meet the more severe service environment of current components.The main conclusions obtained from the paper are as follows:（1）The nitrogen flow rate significantly affected the surface cross-sectional morphology and crystalline structure of the MoN coatings.All four coatings prepared at different nitrogen flow rates had a dense and defect-free structure,and the crystalline phase structure of the coatings changed from Mo phase to Mo₂N phase with increasing nitrogen flow rate.The coatings all have excellent hardness（above 20 GPa）and bonding force（above 60 N）.The MoN coatings prepared by optimizing the regulation of nitrogen flow rate exhibited the lowest friction coefficient of～0.27 and the lowest wear rate of 5.7×10^-8mm³/（N·m）in dry friction conditions.At the meantime,the friction transfer behavior of nitride-based nano-twisted spiral fiber debris appears during the friction process,which has a positive impact on the friction and wear of the coating.（2）The bias voltage significantly affects the structure and properties of the MoN coating.With the increase of bias voltage,the MoN coating cross section changes from a distinct columnar crystal structure to a more dense crystal structure,and the coating exists mainly as a face-centered cubic Mo₂N phase.The hardness of the MoN coatings gradually increased with the increase of bias voltage,and all four coatings prepared at different bias voltages had better film base bonding.The coatings with a bias voltage of160 V showed the lowest wear rate of 1.4×10^-8mm³/（N·m）due to the increase in bias voltage resulting in a denser structure,higher hardness and better wear resistance.（3）Compared to the MoN coatings prepared by DCMS,the MoN coatings deposited through Hi PIMS exhibit a denser microstructure,resulting in higher hardness and lower wear rates.As the peak current increases,the MoN coatings show the growth of columnar crystals with increased crystallinity,and the coatings are mainly existing in the face-centered cubic Mo₂N phase structure.The MoN coating with a peak current of260 A has the lowest friction coefficient of about 0.3,which is better than the MoN coating prepared with DCMS.The MoN coating with a peak current of 300 A has excellent wear resistance with the lowest wear rate of 5×10^-8mm³/（N·m）.（4）The doping of Si elements has a significant effect on MoN coatings,and when the Si content increases to 23.3 at.%,the columnar structure disappears and the coatings exhibit a featureless dense amorphous structure.Meanwhile,proper Si doping can enhance the hardness,elastic modulus and bonding force of Mo Si N coatings.Moreover,the Mo Si N coating with Si content of 23.3 at.%has the best oxidation resistance compared to the other coatings,with no oxidative erosion failure at 600°C.The Mo Si N coating with Si content of 10.4 at.%has the best wear resistance compared to the other coatings.Thanks to the excellent mechanical properties,the Mo Si N coating with Si content of 10.4 at.%has the best wear resistance with the lowest friction and wear rates of around 0.3 and 4.9×10^-8mm³/（N·m）,respectively.