Study On Microstructure And Properties Of CrN Series Coatings Prepared By Plasma Enhanced Magnetron Sputtering

The hard coating represented by the CrN series is widely used in the fields of cutting tools,moulds,aerospace and decoration due to its high hardness and wear resistance,high temperature oxidation resistance and corrosion resistance.Magnetron Sputtering is a common preparation technique for CrN coatings,however,the low（about 10%）plasma ionization rate of the traditional dc magnetron sputtering limits the further development of the coatings,New plasma-enhanced magnetron sputtering technology allows for significant enhancement of plasma density and improvement of coating quality.In this paper,the plasma-enhanced magnetron sputtering technology was used to prepare the CrN series coating,and the influence of the technological parameters on the microstructure,mechanical properties and high temperature tribological properties of the coatings was studied,and compared with the conventional magnetron sputtering coatings.The results are as follows:（1）By adjusting the technological parameters of the CrN coatings prepared by PEMS,it was found that with the increase of discharge current I_D（0A～4A）,the ion current on the substrate surface increases obviously,and the coating hardness increases gradually(1626HV_10g～2382 HV_10g).Under the condition of 4A,with the increase of substrate bias（-10V～-120V）causes the coating to change from（111）preferential orientation to non-preferential orientation.The grain size is significantly refined.The residual stress increased significantly,and the hardness increased to 2884HV_10g.The increase of deposition temperature（14℃～400℃）gradually enhanced the degree of preferential orientation of the coating（200）,the grain size varied from 9.2nm to 12.6nm,and the hardness was as high as 2812 HV_10g.（2）The CrN coatings with thickness of 3.5μm,5.5μm and 7.0μm were deposited by PEMS and DCPMS respectively.Firstly,with the increase of thickness,the PEMS coatings are（111）preferentially orientation,the hardness increases to 4391HV_10g,and the grain size increases first and then decreases.Secondly,compared with DCPMS coatings,PEMS CrN coatings had higher hardness,lower corrosion current density,the corrosion resistance of 3.5wt.% NaCl solution was better,and lower residual stress at high thickness（7.0μm）.（3）CrAlAgN coatings was deposited by plasma-enhanced magnetron sputtering with a Ag content of 8.25 at.%.The coating presented a single fcc Cr Al N phase structure with（111）preferential orientation,consisting of fine columnar crystals with a hardness of 2586HV_100g.The high temperature tribological test of the coating was conducted at 500℃～900℃.It was found that Ag particles were precipitated on the surface of the wear track,which played a certain role of self-lubrication.Friction coefficient decreases from 0.77（500℃）to 0.5（600℃～900℃）.The wear rate of coating is the lowest at 500℃,which is 0.39×10^-5mm³/Nm,and the wear rate of the coating fluctuated between 3.82×10^-5mm³/Nm and 6.47×10^-5mm³/Nm at600℃～800℃,while at 900℃,the wear rate of the coating increased to 7.98×10^-5mm³/Nm,about twice as much as at 800℃.With the increase of temperature,the hardness of coating showed a downward trend on the whole,and the hardness of coating at 900℃decreased by32% compared with untreated.In conclusion,the CrN series coatings with good structure density and performance can be prepared by PEMS at the appropriate bias pressure and deposition temperature.The deposited CrAlAgN coating shows good wear resistance at high temperature.The coatings prepared by this technology is more suitable for use under complex working conditions.