Research On Interfacial Bonding Properties Of Tialn Coated Carbide Tools Based On First Principles

TiAIN coated carbide tools become one of the most widely used carbide coated tools because of their excellent comprehensive mechanical properties,which can effectively improve the machining efficiency and tool life.Domestic and foreign scholars have studied TiAIN coated carbide tools mainly for the macroscopic interfacical bonding performance of the tool,and there have been few studies on the microscopic mechanism of the internal interface between coating and substrate.In the paper,based on the first principle,the internal interfacical bonding property of the TiAIN coated WC-based carbide tools is studied.The internal microcosmic bonding mechanism of the interface is analyzed.The research results are of great theoretical and practical significance for the realization of the optimized design of coated carbide tools.In the TiAIN coated WC-based carbide tools,cemented carbide substrate mainly includes hard phase WC and binder Co.The content of WC is much larger than that of Co,and the interfacial bonding property between WC and TiAIN plays a leading role in the interfacial bonding property between coating and substrate.In this paper,the interfacial bonding properties between the hard phase WC and the TiAIN coating are mainly studied.Nine kinds of TiAlN/WC ideal interface molecular dynamics models are established.The interface mismatch and interfacial bonding energy of these nine interface models are calculated.The results show that the maximum bonding energy of TiAlN(100)/WC(001)interface is 3.829 J/m2,and the interfacial bonding property is the most stable.The minimum bonding energy of TiAlN(100)/WC(001)interface is 2.441 J/m2,and the interfacial bonding property is the most unstable.In addition,the electronic structure of the interface model is analyzed.At the atomic level,the nature of interfacial bonding is explored.Based on the TiAlN(001)/WC(001)ideal interface model with the worst interfacial bonding performance,the interface model with different doping atoms X(X=AI,Cr,Ti,Ta,Nb,Co)is established.The interfacial bonding properties of different atom doped interfaces are calculated.The results show that the doping of Al,Co and Cr atoms can improve the interfacial bonding properties.When the Ti,Ta and Nb atoms are doped,the interfacial bonding performance becomes weaker.The electronic structure of the interface model doped with Al Ta and Co atoms is analyzed.It is found that Al atoms lose free electrons,Al and N atoms form a bonding bond.There are more local spikes near the Fermi level,which makes the interfacial bonding performance better.The local spikes at the Fermi level of the doped a Ta atom is more sharp,the interfacial bonding performance is weak.The charge density around Co atoms is larger,and enhancing the interfacial bonding properties.Based on the TiAlN(001)/WC(001)ideal interface model with the worst interfacial bonding performance,the interface model with different vacancy atoms Y(Ti,Al,N,W,C)are established.The interfacial bonding performance,the interfacial bonding energy are calculated.The results show that single atom vacancy defect can cause the interfacial bonding property to decrease.The interfacial bonding performance of a W atom is the worst.The electronic structure of the interface model with a W atom vacancy defect is analyzed.The results show that the W atom has strong bonding with N atoms,the main local spikes shifts to the right,and the interfacial bonding property decreases.The interfacial bonding energy of a C atom with a atom vacancy is maximum and the interfacial bonding performance is relatively stable.When the crack occurs at the vacancy defect of W atom,the crack easily extended to the C atom at the interface.Based on the multiple vacancy defects between the coating/substrate interface,which are micro cracks,four supercell interface models of different types of microcracks are constructed,including parallel interface crack 1W-2C,parallel interface crack 1N-2Ti,vertical interface crack 1N-1Ti-1C and slanting interface crack 1N-2C.The percentage of interfacial bonding energy and the atomic vacancy defect interfacial bonding energy of the above models are calculated.The results show that the interfacial bonding energy of parallel crack 1W-2C is the smallest,which makes the interfacial bonding performance weakest.Under the external load,the microcrack is easier to expand from here.