Study On Interfaces First-principles Cauculation Of TiN Films Based On WC

The technology of coating plays an important role in improving the performance of high precision cutting tools.TiN coated cutting tools have better mechanical properties than ordinary tools and are widely used.According to engineering experience,the bonding quality of TiN coating to HSS substrate is better than that of TiN coating to cemented carbide.However,is less known that the bonding mechanism of TiN coating to substrate,which is not help to draw up about the coating materials and formulation of coating process.Therefore,this work to analyze TiN/cemented carbide and TiN/high-speed steel to carry out a series of simulation analysis and experimental research on the binding mechanism of TiN coating and substrate.WC(0001)/TiN(111)interface model and Fe(100)/TiN(111)interface model were bulided in Materials Studio.The geometrical structure of the interface model was optimized in the CASTEP module,and the binding energy and electronic structure of the WC(0001)/TiN(111)interface and the Fe(100)/TiN(111)interface were analyzed.Considering the interfacial binding energy of W-OT-Ti,W-(OT,MT)-N,C-HCP-Ti and C-(MT,HCP)-N,the interface binding energy of C-HCP-Ti is the highest,W-OT-Ti is the next,and W-OT-N is the lowest.Considering the interface binding energy of Fe-HCP-Ti and Fe-(OT,MT,HCP)-N,the interface binding energy of Fe-HCP-Ti is the highest,followed by Fe-OT-N and Fe-OT-Ti is the lowest.Then,the electronic structures of the interface mentioned above are analyzed.C-HCP-Ti interface bonding mode is strong covalent bond,and the bond strength is the strongest.W-OTTi interface bonding mode is covalent bond and partial metal bond,the bonding strength is the second.For W-OT-N interface,the interfacial bonding strength is weak covalent bond,and the bonding strength is relatively weak.In other words,metal bonds exist in the three interface structures of Fe-HCP-Ti,Fe-OT-N and Fe-OT-Ti,and covalent bonds may exist in the interface structure of Fe-HCP-Ti.Finally,TiN films were prepared on cemented carbide and stainless steel specimens and the microstructure,roughness,bonding strength,hardness and other mechanical properties of the coatings were observed.It is concluded that the TiN coating surface morphology is uniform and dense without large particles,and its distribution in stainless steel substrate is more uniform than that in cemented carbide substrate.After TiN coating,the surface roughness of the sample is significantly reduced,and the surface roughness of TiN/ stainless steel is smaller and more smooth.It is found that the bonding strength of TiN coating with cemented carbide and stainless steel is HF1-HF3 and HF0,respectively.The bonding strength between TiN coating and stainless steel is better than that between TiN coating and cemented carbide.It can be seen that the hardness of the coating was significantly improved by TiN coating,and the microhardness of the surface of TiN/ cemented carbide was higher than that of TiN/ stainless steel.