Microstructure And Property Analysis Of CrAlSiN Nano-gradient Coating

Titanium alloy,superalloy and other refractory materials and are widely used in aerospace and other fields.But they have low thermal conductivity,so that the cutting force and cutting temperature on the tool is very high,accelerate the tool wear.CrAlSiN coating has good mechanical properties,wear resistance and high temperature oxidation resistance,and is widely used in cutting tools.However,when the content of Al and Si is high,the coating has great brittleness,low binding force and is prone to flake off.If gradient structure design is adopted,the gradient change of Al and Si content can reduce the difference between CrAlSiN coating and tool matrix,which is expected to solve this problem.In this paper,four kinds of CrAlSiN nanocomposite coatings with different Al contents were prepared by using high-power pulsed magnetron sputtering(Hi PIMS)and DC magnetron sputtering(DCMS)composite technologies to change Al target power,and the effect of Al target power on the structure and performance of the coatings was studied.Three kinds of CrAlSiN nanocrystals with different Al and Si contents on the surface were prepared by DCMS and arc ion plating(AIP).The effect of Al and Si contents on the microstructure,mechanical properties and cutting properties of the nano-gradient coatings was studied.The CrAlSiN nano-gradient coating and the CrAlSiN nanocomposite coating were compared,and the effect of the gradient structure on the microstructure and mechanical properties of the coating was analyzed.The main research results are as follows:Four kinds of CrAlSiN nanocomposite coatings with different Al content were prepared by changing Al target power.It is found that the four coatings all have fcc-Cr N phase and amorphous phase Si₃N₄.The coatings are all(200)crystal surface oriented and have columnar crystal structure formed by epitaxial growth.With the increase of Al target power,the grain size of the coating gradually decreases.However,when Al target power reaches 1.2k W,small particles aggregate into large particles,resulting in the increase of surface roughness and more holes.When Al target power is 0.8 k W,the coating has the best mechanical properties because of the largest H(26.7GPa),E^*(383.5GPA),H/E^*(0.0696),H³/E^*2(0.1296),We(55.85%)and binding force(27.8N),CrAlSiN nano-gradient coatings with different Al and Si content on the surface were prepared by different terminal power of Cr Al Si target by the method of increasing target power linearly.It is found that the main phase structure of the coating is fcc-(Cr,Al)N phase,and the preferred orientation changes from(111)to(220)plane with the increase of linear terminal power of the Cr Al Si target.The hardness of the coating gradually increased from 28.07GPa to 30.44GPa.CrAlSiN coatings with target power of 0.6-2.8k W have the highest H/E^*,H³/E^*2 and We values,which are 0.060,0.109 and 51.79%,respectively.The number of Vickers-indentation edge crack is less,and the extension is not obvious,thus it has the best plasticity and toughness.With the increase of the linear terminal power of the Cr Al Si target,the life of the three CrAlSiN nano-gradient coated tools will be prolonged.Taking VB=0.1mm as the blunt standard,the cutting length of 0.6-1.2k W,0.6-2.0k W and 0.6-2.8k W coated milling cutter is 44min,82min and 95min,respectively.CrAlSiN nano-composite coatings were prepared by constant Cr Al Si target power and compared with gradient coatings.The results show that the CrAlSiN nano-composite coating grows along the(220)crystal plane,and the Si content is high,and the hcp-Al N phase in the coating is reduced because of the more amorphous Si₃N₄ phase.The values of H/E^*(0.058)and H³/E^*2(0.099)of CrAlSiN nano-gradient coating are higher,and it has better elastic and plastic deformation resistance.At the same time,CrAlSiN nano-gradient coating has high adhesion due to the continuous change of composition and structure.As the friction exceeds 3000r,the friction coefficient of CrAlSiN nano-gradient coating increases,which accelerates the coating wear to some extent.Therefore,the wear rate of CrAlSiN nano-gradient coating is slightly higher than that of CrAlSiN nano-composite coating.