Study On In-Situ Preparation Of Aluminum Nitride Layer On Aluminum Substrate Surface Based On Ion Nitride Technology

Aluminum nitride（Al N）is a new ceramic material with excellent comprehensive properties,such as high thermal conductivity（320 W/m K）,good corrosion resistance,high resistivity,high hardness and wear resistance,having a broad application prospect and broad potential market in the electronic,electric power,locomotive,aerospace,national defense,military project,communications and many industrial fields.The Al N layer formed on the surface of aluminum matrix can effectively improve its wear resistance,expanding the application of aluminum in semiconductor and electronic industries.The aluminum nitride layer can be deposited directly to the substrate surface by traditional methods,including dc reactive magnetron sputtering method,chemical vapor deposition,plasma spraying method,plasma immersion ion implantation method,etc.The bond force between the nitride layer and substrate is weak.While through the method of plasma nitridation,the aluminum nitride layer can directly form the infiltration layer in the form of in-situ reaction,with better binding force.The application technology of plasma nitriding on steel surface has become mature,which has the advantages of fast nitriding speed,short production cycle,small deformation and low nitriding temperature.Therefore,it is of great significance to form al nitride layer on Al base surface by ion nitriding method.In this paper,aiming at the problem that the oxide film on the surface of aluminum prevents the infiltration of nitrogen atoms and formation the aluminum nitride layer,the oxide film was removed by bombarding the surface of aluminum firstly,and then the nitride treatment was carried out to obtain the aluminum nitride permeable layer with the thickness of 6～7μm on pure aluminum substrate.XRD,SEM,EDS and 3D morphology were used to analyse the surface of the bombarded samples and the permeable layer after ion nitride,and the corrosion resistance and wear resistance of the permeable layer after ion nitride were also studied.It provides an effective attempt and basic research for ion nitriding treatment of aluminum and its alloy surface.The main results of the experiment are as follows:（1）Pretreatment by ion bombardment to remove oxide films from aluminium surfaces.Argon and hydrogen were used as gas sources,and the removal effect of oxide film on the surface was observed by changing the gas composition and content,the time and temperature of the bombardment.The treated surface in an atmosphere of Ar:H₂=1:1（the volume flow rate of both argon and hydrogen was 0.25 slm）,with a bombardment temperature of 480°C and a bombardment time of 1.5 h,was more favorable for the post-nitriding treatment.（2）The influence factors of the formation of ion nitriding layer on the surface of aluminum samples were studied by changing the nitriding gas,furnace pressure,nitriding temperature and time.The results are as follows:When N₂:H₂=3:1（the volume flow of nitrogen and hydrogen is 0.75 slm and 0.25 slm,respectively）,the furnace pressure is 265 Pa,the nitriding temperature is 480°C and the temperature is held for 24 h,a nitriding layer with thickness of 6～7μm can be obtained in the nitriding atmosphere.The infiltration layer is composed of Al N of cubic sphalerite structure and face-centered cubicα-Al phase,with a sample surface hardness of 213.5 HV.（3）XPS and EPMA analyses were carried out on the surface of pure aluminum and nitriding samples treated for 24 h,and the formation mechanism of nitriding layer on the surface of aluminum matrix was investigated.（4）The nitride samples obtained under different technological conditions were immersed in 1N HCl and placed for different time.The corrosion resistance of the nitride layer was investigated according to its weight loss,and then the corrosion mechanism of the nitride layer was studied.The results showed that the minimum weight loss was achieved under the nitriding temperature of 480°C and holding temperature for 24 h.By observing the surface morphology of the sample after corrosion by SEM,it can be seen that the dense al nitride layer formed on the surface is the reason for improving the corrosion resistance.（5）Nitrided specimens under different process conditions on the friction and wear experiment,found 480°C for 24 h nitride sample smooth curve and friction coefficient under the condition of minimum number of samples after the SEM observation of the wear surface grinding crack morphology and three-dimensional grinding crack depth,narrow and shallow,its surface grinding marks show that the aluminum nitride formed by the process of infiltration layer has good abrasion resistance.Therefore,in order to improve the friction and wear resistance of the sample surface,it is necessary to form a dense and thick nitriding layer on the aluminum base surface.