Study On The Comprehensive Properties Of CrAlN Based Hard Coatings By Multi Arc Ion Plating

Transition metal nitride coatings are widely used in fields such as cutting tools,molds,and automotive components due to their excellent hardness,film based adhesion,and service life.The most representative among them is the CrAlN ternary coating,but its relatively poor high-temperature thermal stability and high-temperature oxidation resistance limit its use in special processing environments.On the basis of orthogonal experiments,CrAlBN coating,Cr Al Si WN coating,and CrAlBN/Cr Al Si WN nanocomposite coating were prepared using a multi arc ion plating equipment.The effects of various process parameters on the coating performance were studied,as well as the microstructure,mechanics,tribology,thermal stability,and oxidation resistance of the coating under the optimal process parameters,Finally,a commercial coating with excellent mechanical properties and excellent high-temperature thermal stability and high-temperature oxidation resistance was obtained.The specific research results are as follows:（1）The optimal process parameters for CrAlBN coating obtained through orthogonal experimental scheme are:arc current 150 A,rotational speed 3 r/min,negative substrate bias voltage-50～-150 V,and duty cycle 80%.The CrAlBN coating was prepared under the optimal process parameters.According to the results of XRD and XPS,it can be concluded that the CrAlBN coating prepared in this paper consists of c-Cr N phase,c-Al N phase,and BN phase.The film thickness of the coating is 5.4 microns,the friction coefficient is 0.441,the film based bonding force is 90 N,and the microhardness is 3517.4 HV.The amorphous BN phase increases the hardness of the coating.The thermal stability test results showed that the coating did not fail at 1200℃,and the microhardness of the coating at this temperature was 1600 HV.The reason for obtaining higher thermal stability was that the doping of B element inhibited the thermal decomposition process of CrAlN coating,delaying the formation of h-Al N phase and h-Cr₂N phase.The antioxidant test results indicate that the coating still has functionality at 1100℃,and it is not until 1250℃that the coating surface is completely oxidized and the coating fails.（2）The optimal process parameters for Cr Al Si WN coating obtained through orthogonal experimental scheme are:arc current 150 A,rotational speed 2 r/min,negative substrate bias voltage-50～-200 V,and duty cycle of 80%.The Cr Al Si WN coating was prepared under the optimal process parameters.According to the results of XRD and XPS,it can be concluded that the Cr Al Si WN coating prepared in this paper consists of c-Cr N phase,c-Al N phase,c-WN phase,and Si₃N₄phase.The film thickness of the coating is 4.7 microns,the friction coefficient is 0.478,the film based bonding force is 86.36 N,and the microhardness is 3817.4 HV.The amorphous Si₃N₄phase improves the mechanical properties of the coating.The thermal stability test results indicate that the coating fails at1200℃.The antioxidant test results indicate that the coating still has functionality at1100℃,and it is not until 1250℃that the surface of the coating is completely oxidized and the coating fails.The doping of Si element can form a nanocomposite structure,promoting the formation of Al₂O₃at high temperatures.（3）The CrAlBN/Cr Al Si WN nanocomposite coating was prepared by selecting the optimal preparation process for each of the two coatings.The film thickness is 6.3 microns,the film based adhesion force is 101 N,the friction coefficient is 0.433,and the microhardness is 4102.36 HV.The adhesion force and microhardness of the nanocomposite structure film have been significantly improved compared to the single-layer film.The thermal stability analysis results show that the CrAlBN/Cr Al Si WN nanocomposite coating still fails at 1200℃,and the hardness of the coating is 2001.23 HV at this temperature,which is improved compared to the single-layer film.The oxidation resistance temperature did not decrease until 1250℃,when the coating surface was completely oxidized and the coating failed.The overall mechanical properties of the prepared CrAlBN/Cr Al Si WN nanocomposite coating have been improved,while also possessing the thermal stability and oxidation resistance of both CrAlBN and Cr Al Si WN coatings.