Research On The Microstructure,Mechanical Properties,thermal Properties And Corrosion Resistance Of AlN/TiAlN Multilayers

TiAlN coating is widely used as cutting tool coating because of its excellent thermal stability and high hardness.However,its oxidation resistance needs to be improved to meet the harsh service for nowadays industry.We systematically investigate the effect of Al content on structure as well as mechanical properties,thermal properties（thermal stability and oxidation resistance included）and corrosion resistance of TiAlN coatings.Based on the existing research of TiAlN monolitithic coatings,AlN/TiAlN multi-layer coatings was designed,to make the w-AlN grow coherently with c-TiAlN（template effect）,which further improve the properties of TiAlN coatings.Then we investigate carefully the effect of AlN layer as well as AlN content of TiAlN on multilayer coatings.This studies improve the basic properties of TiAlN coating,and compare the relationship between the composition,structure and properties of TiAlN coating in detail.In addition,we also provides a new direction for studying the template effect of multilayer coating The main conclusions are as follows:（1）All of TiN,Ti_0.55Al_0.45N,Ti_0.44Al_0.56N and Ti_0.38Al_0.62N coatings exhibit a face-centered cubic（fcc-）structure.With the increase of Al content,the hardness values of Ti_1-xAl_xN continue to increase from～26.4GPa for TiN to～28.6GPa for Ti_0.55Al_0.45N to～30.5 GPa for Ti_0.44Al_0.56N to～32.7 GPa for Ti_0.38Al_0.62N.The addition of Al promotes the thermal decomposition process of the coatings.The oxidation resistance of TiAlN coating increased first and then decreased slightly,with the introduction of Al atom.Ti_0.44Al_0.56N coating has the best oxidation resistance.In addition,the introduction of Al reduces the corrosion resistance of the TiN coating,but the corrosion resistance of Al-containing coatings increases with increasing Al content.（2）Based on the template effect,AlN（hexagonal wurtzite structure）layers invidually grow epitaxially with c-TiN and Ti_0.55Al_0.45N layers,followed a sigle-phase face-centered cubic（fcc-）structure and increased hardness values of～30.5GPa for AlN/TiN and～31.4 GPa for AlN/Ti_0.55Al_0.45N.However,AlN/Ti_0.38Al_0.62N reveals the double phase structure composed of face-centered cubic and hexagonal wurtzite.AlN layers promotes the thermal decomposition process of the coatings.The oxidation resistance of multilayer coatings are related to the Al content of TiAlN template layers,closely.And AlN layers improve the oxidation resistance of the coatings.After oxidation at 850℃for 10 h,AlN/Ti_0.38Al_0.62N reveal oxide layers of～2.5μm,which is thiner than AlN/Ti_0.55Al_0.45N of～3.5μm.In addition,AlN/Ti_0.38Al_0.62N shows the best corrosion resistance.