Research Of Preparation Process And Properties Of CrAlN Films Deposited On Alumium Alloy By Filtered Cathodic Vacuum Arc Technology

Aluminum alloys have been widely applicated in various fields such as architecture,aviation,navigation and rail traffic due to excellent properties of low density,high specific strength and easy forming,exhibiting a broad application prospect.However,the disadvantages of low hardness and poor corrosion resistance seriously limit further application in special working conditions.As a kind of ternary hard film,CrAlN films contain Cr element for thermal anti-corrosion,which is intelligent films with both wear resistance and thermal corrosion resistance.Nevertheless,the oxidation films on the aluminum alloy surface and the mismatching of mechanical and thermal properties with CrAlN films hinder the growth and bonding of CrAlN film on the aluminum alloy in common.Therefore,how to obtain the uniform and dense films with high adhesion force of films is the key point of CrAlN films modification on aluminum alloy.In this paper,a series of CrAlN films with different process parameters and structure designs were prepared on the aluminum alloy by Filtered Cathodic Vacuum Arc technology?FCVA?.The effects of the process parameters?nitrogen pressure,substrate negative bias?,gradient structure and multi-layer structure design on the morphology,mechanical properties and adhesion of CrAlN films were studied.The conclusions are as follows:1.All films present c-CrAlN face centered cubic structure and the films phase composition are consist of AlN phase,CrN phase and Cr₂N phase.With the increase of nitrogen pressure and negative substrate bias,the films dominant phase changed consequentially.The films present a wavy morphology similar to water ripples and the cross section shows the columnar morphology of polyphase growth competition.In addition,the primary silicon contained in the substrate seriously affects the films surface state.The phase composition and stress state of the films ultimately determine the film's performance.Combined with the film's surface morphology,in the case of negative substrate bias is 50 V and the nitrogen pressure is 0.05 Pa,the films present the best interface bonding performance with 10.39 N.2.Nitrogen content gradient structure designs have little influence on the deposited CrAlN films phase structure.Nitrogen content gradient structure designs of the deposited CrAlN films on aluminum alloy can effectively remit the lamellar fracture phenomenon.In nitrogen content gradient structure designs of CrAlN gradient films,the films at the case of 0.05/0.06 Pa s present the best interface binding performance,the binding force reaches 16 N.3.In the multi-layer structure design of CrAl/CrAlN films,with the increase of the film layers number,excessive nitrogen reacts with Cr ion and reacts with Al-Si alloy through grain boundary,the films phase composition changes from AlN?200?to AlN?200?+Cr2N+Six N consequentially.The phase composition and stress state of the deposited CrAl/CrAlN films determine the surface state and bonding performance.Among the multi-layer structure design,CrAl/CrAlN films with double layers present the best interface bonding performance with 8.04 N.