Research On Properties Of TiAlN Coated Based On First-principles

TiAlN coating not only has high hardness,excellent oxidation resistance and wear resistance,but also has good thermal hardness,low friction coefficient and other excellent properties,so TiAlN coating cutters are widely used in cutting processing.The chemical composition and microstructure of the coating are the main reasons for the coating performance.For TiAlN coating,the coating is based on Ti N coating with the addition of Al elements,where the content of Al elements affects the structure of TiAlN.In this paper,the effect of Al content on the electronic structure and mechanical properties of Ti_1-xAl_xN is investigated based on the first nature principle,and the correctness of the simulation calculation results is verified through macroscopic experiments,and TiAlN coated inserts are prepared based on the needs of actual production,their life span is examined through cutting experiments,and the wear mechanism is analyzed.In order to investigate the effect of Al content on the electronic structure of Ti_1-xAl_xN,the cell models of Ti_1-xAl_xN with Na Cl face-centered cubic structure and hexagonal wurtzite structure with different Al contents were constructed by CASTEP module in Msterials Studio software on the basis of Ti N and Al N unit cells by replacing Al and Ti atoms with each other.The effects of Al content on the lattice constant,formation energy,band structure and density of states of Ti_1-xAl_xN were calculated and analyzed.The results show that the lattice constant of Ti_1-xAl_xN tends to decrease with the increase of Al content,the absolute value of formation energy gradually decreases with the increase of Al content,the structure of Ti_1-xAl_xN tends to be stable,and the electronic structure analysis shows that Ti_1-xAl_xN always shows metallicity.The elastic constants of Ti_1-xAl_xN were calculated and the effect of Al content on the mechanical properties of Ti_1-xAl_xN was analyzed using the CASTEP module in the Msterials Studio software.The hardness values of Ti_1-xAl_xN for two structures were calculated by empirical equations to analyze the effect of Al content on hardness and to build a link between microstructure and macrohardness.The results show that for Ti_1-xAl_xN with Na Cl-type face-centered cubic structure,the material exhibits brittleness,which decreases with increasing Al content,and the ability of the material to resist plastic deformation and stiffness increases,but the ability to resist fracture decreases;for Ti_1-xAl_xN with hexagonal fibrous zincite structure,the material exhibits toughness,which decreases with increasing Al content,and the ability of the material to resist plastic deformation and stiffness increases.With the increase of Al content,the hardness value of Ti_1-xAl_xN tends to increase,but when the value of Al content is 25at%,the ability of the material to resist plastic deformation and stiffness is the smallest,and the hardness value also reaches the lowest,when the Al content reaches 75at%,the hardness value of Ti_1-xAl_xN reaches the maximum,and when the Al content is greater than 75at%,the hardness value starts to decrease.Overall,the mechanical properties of Ti_1-xAl_xN with face-centered cubic structure are better than those of Ti_1-xAl_xN with hexagonal fibrous zincite structure.Ti_1-xAl_xN coatings containing Ti_0.5Al_0.5N and Ti_0.33Al_0.67N were prepared by arc ion plating.The surface and microstructure of Ti_1-xAl_xN coatings were characterized by scanning electron microscopy.The mechanical properties and coating binding force were detected by nanoindentation instrument and scratch test.The hardness values of Ti_1-xAl_xN corresponding to Ti_1-xAl_xN in Chapter 3 were verified.The experimental results show that with the increase of Al content,the surface droplet phenomenon increases,the surface roughness increases,and the surface quality decreases.By testing the mechanical properties of the coating,the hardness of the coating increases with the increase of Al content,and the wear resistance and plastic deformation resistance increase,but its binding strength decreases with the increase of Al content.Three kinds of TiAlN coated blades were prepared by arc ion plating technique.The life and wear of the coated blades were studied by cutting experiment,and the mechanism was analyzed.The experimental results show that:the number of TiAlN coated inserts produced independently cutting workpieces is more than that of the same Teguc inserts in the market,the tip of the insert is easy to form chip tumors during the cutting process,the surface of the insert has a furrow area,and the wear mechanism is mainly abrasive wear.Comparing the cutting life of inserts prepared by PVD technology and CVD coating technology,it is found that the life of inserts prepared by PVD coating technology is better than that of CVD coated inserts.Under the experimental machining conditions of this thesis,the coated inserts prepared by PVD technology can replace the CVD coated inserts of the same model.