The Investigation On Properties Of The TaN/TiN Multilayer Coatings Prepared By Multi-Field Vapor Depositon

Modern machining has put forward comprehensive performance requirements for cutting tools,such as high hardness,wear resistance and oxidation resistance,and ordinary cutting tools have been difficult to meet the machining requirements.Coating a layer of hard film on the surface of cutting tools can significantly improve the service life,cutting speed and machining accuracy,and greatly enhance the durability,applicability and machining reliability of cutting tools.Therefore,the tool hard coating has been widely studied as a research focus.Since the advent of the first generation of TiN coatings,hard coatings have developed rapidly in the direction of diversification and structural complexity.So far,there are many kinds of hard coatings with various functions.However,the requirements of hard films in high-end manufacturing are more stringent,and there is an urgent need to develop more advanced coating systems,so Ta series of hard coatings emerge as the times require.At present,most of the reports on Ta thin films are prepared by DC magnetron sputtering,which is still in the stage of laboratory testing.Therefore,the purpose of this paper is to prepare TaN/TiN multilayer films by industrial multi-arc ion plating（AIP）and high power impulse magnetron sputtering（Hi PIMS）,to study the effects of different preparation methods on the phase composition,microstructure and mechanical properties,tribological properties and corrosion resistance of multilayer films,to discuss the relationship between the structure and properties of materials,and to explore the possibility of combining multi-arc ion plating+high power impulse magnetron sputtering.AIP-TaN/TiN multilayer films with h-TaN/c-Ta Ti/c-TiN sandwich structure were prepared at various target-substrate distance(d_ts)from 180 to 240 mm.The maximum hardness of the AIP-TaN/TiN multilayer film is 29.0 GPa.With the increase of d_ts,the H,H/E and H³/E² of the film decrease firstly and then increase,while the adhesive strength showed an opposite trend.When the d_ts=200 and 220 mm,the film has the maximum adhesion of 69 N and 68 N.When the d_ts=220 mm,the film has the lowest friction coefficient and wear rate,which are 0.41 and 2.7×10^-6 mm³（m N）^-1,respectively.When the d_ts=220 mm,the maximum E_corris-0.2088 V and the minimum I_corr is 0.9811×10^-7 A/cm²,showing the best corrosion resistance.h-TaN/c-TiN multilayer films with modulation periods of 336,168,112 and 56 nm were prepared by Hi PIMS.The hardness of TaN/TiN multilayer films increases linearly with the decrease of modulation period,and the maximum hardness is 20.5 GPa at 56nm.The bonding strength of Hi PIMS-TaN/TiN films is excellent,all of them are of HF1.Due to the high toughness of the films,there are only circumferential cracks around the indentation.With the decrease of the modulation period,the hardness of the film increases,resulting in the decrease in friction coefficient and wear rate,indicating the increase in wear resistance.The defects in the film are easier to penetrate the single-layer film,thus providing pathes for etching.Therefore,with the decrease of the modulation period,the trend of self-corrosion increases.On the contrary,more layers provide a large number of stable interfaces and prolong the corrosion diffusion path.Therefore,the Hi PIMS-TaN/TiN multilayer films with lower modulation period show higher durability in the corrosion process.h-TaN/c-TiN multilayer films with AIP-TiN+Hi PIMS-TaN design were prepared by multi-field composite deposition technique（Hybrid）.The thickness of the thin film is 1.46～1.64μm under the bias voltage of 100～200 V.with the increase of bias voltage,the electric field force and bombardment effect are enhanced,so the thickness of the film increases firstly and then decreases.The friction coefficient of Hybrid films is 0.45～0.46,and the maximum depth of each wear mark does not exceed the thickness of the film,which shows excellent wear resistance.With the increase of bias voltage,the corrosion resistance increased firstly and then decreased,and the Hybrid-TaN/TiN film at 130V has the best corrosion resistance.Among the three kinds of films prepared by different PVD techniques,the Hi PIMS-TaN layer in Hybrid weakens the adverse effects of large droplets and pits in AIP-TiN layers,so that the Hybrid films have high hardness and smooth surface with fewer defects.The friction mode of AIP and Hi PIMS film is typical abrasive wear,the wear mode of Hybrid film is abrasive wear and adhesive wear,and Hybrid film has the best wear resistance.Hi PIMS films show the highest E_corr and the lowest I_corr,AIP and Hybrid films have the similar corrosion resistance.However,due to the more stable interface and tight interfacial connection without voids,the corrosion resistance of AIP films is more durable under continuous corrosion,followed by Hybrid films,and the durability of Hi PIMS films is the lowest.Therefore,the Hybrid technology realizes the combination of AIP and Hi PIMS.