Study Of Properties On TiN Based Nanocomposite Multilayer Coatings Deposited By Multi-arc Ion Platings

The hard coating represented by TiN is widely used as a surface modification material for cuttings tools and moulds,because of its high hardness,good wear resistance and chemical stability.However,in recent years,the rapid development of new cutting processes such as dry cutting and high-speed cutting often requires coating tools to work in harsh production environments such as high temperature,heavy load and high impact frequency.The properties of Traditional TiN films cannot meet the demands of these cutting processses.People fabricate single-layer TiN film into nano-multilayer films with interfacial effects and interlayer coupling effects.;A multi-alloyed or super-lattice structure nanocomposite film is prepared in a diversified manner.This two films all performed superior mechanical properties than the single-layer TiN film.In order to combine the advantages of the two coatings,three different TiN-based nanocomposite multillayer films were prepared on the cemented carbide substrate by multi-arc ion plating:Ti/TiN multilayer films,TiCu/TiN-Cu multilayer films and CrN/TiN-Cu multilayer films.In this paper,the effects of the modulation period(A)of three composite membranes on the microstructure and mechanical properties of TiN-based nanocomposite multilayers were systematically studied.The membrane materials of the three films were compared and analyzed,and the effect of compositional differences on film properties were studie.The results are as follows:(1)Five groups of Ti/TiN nano-multilayers with a series of modulation period of 5nm-40nm were prepared.The effects of modulation period on the mechanical properties of multilayer films were studied.The superhard effect of Ti/TiN nano-multilayer films at nanometer scale were discussed.The experimental results show that the fracture morphology of the prepared multilayer film is a multi-layer structure with clear interface and no obvious columnar crystal structure.The film is uniform and dense,mainly composed of fcc-TiN phase,and the TiN peak grows preferentially along(111),and the intensity decreases with the decrease of the modulation period.The hardness and elastic modulus of the multilayer film increased first and then decreased with the decrease of the modulation period.At A=7.5nm,the maximum values were simultaneously obtained,which were 42.9GPa and 357.88GPa,respectively.The Ti/TiN nano-multilayer film has the best performance at ?=7.5nm,At this time,H/E value(ratio of microhardness and elastic modulus)is 0.1198,and the adhension is(58.1±0.9)N.The Hall-Petch effect,the modulus difference effect on and the bombardment of the film by the high-energy reaction particles have a good performace in strengthening the film hardness.(2)TiCu/TiN-Cu nano-multilayer films with a series of modulation period of 5nm-63nm were prepared by introducing Cu into Ti/TiN nano-multilayer films.The results show that the content of Cu in the prepared single-layer TiN-Cu film is 2.3 at.%,the cross section is uniform and dense,and there is no columnar crystal structure.However,the surface of the film has defects such as cracks and pits.The TiCu/TiN-Cu multilayer films has a clear multi-interface structure with good surface quality and no obvious defects,but the number of large particles is significantly higher than that of single-layer TiN-Cu film.Compared with the TiN film,the hardness of the single-layer TiN-Cu film increased from 25.5 GPa to 34.2 GPa,and the elastic modulus increased from 302.5 GPa to 342.1 GPa.The hardness of TiCu/TiN-Cu nanocomposite multilayer film increases first and then decreases with the decrease of modulation period,and has the maximum value at ?=13.7nm,which is 42.6GPa.The modulation period of TiCu/TiN-Cu multilayer films is about twice as long as Ti/TiN films' best modulation period,which indicates that increasing the modulus difference of adjacent layers has a strengthening effect on the film' hardness.At ?=13.7 nm,the H/E value of the multilayer films was 0.1247,the film-based bonding force was(49.1±0.8)N,and the average friction coefficient was 0.17,which was the most excellent in overall performance.(3)By replacing the metal layer in the nano-multilayer film with CrN layer,a CrN/TiN-Cu nanocomposite multilayer films with a series of modulation period of 7.9nm-78.7nm was deposited,and the superhard effect of nano-multilayer was studied,and the films were analyzed for the influence of the introduction of Cr on the wear resistance.The results show that the fracture morphology of the film shows that the boundary of the multilayer structure is straight and clear,and the interface quality begins to deteriorate at A=18.7nm,and the delamination disappears as the modulation period continues to decrease.The multilayer film is mainly composed of TiN phase and Cr2N phase,in which TiN mainly grows in the(111)and(200)directions,and Cr2N mainly grows in the(200)direction,and the intensity of the diffraction peaks reduced with the modulation period's decrease.When ?=39.3nm,the CrN/TiN-Cu nanocomposite multilayer films have the best comprehensive performance,and its hardness is 38.2GPa,which is only slightly lower than the best hardness of 40.1GPa at ?=18.7nm This is because the films exist template effect,which reduces the dependence of film hardness on the modulation period.In addition,the introduction of Cr element effectively reduces the adhesive wear of the multilayer film and improves the wear condition.The optimal friction coefficient is 0.12,and the maximum critical load of the film is(52.7±2.3)N.