Preparation And Properties Of Nano-periodic Hard Film On Cemented Carbide Surface

Transition metal nitride thin films have high melting point,high hardness,high toughness characteristics,widely used in mechanical processing.Since the transition metal nitride film appeared,it has undergone a performance monotonous binary film and a variety of performance of the multicomponent nitride film,and now developed to nano-composite structure and multi-layer structure films to meet the needs of higher industrial requirements.In this paper,CrAlN-AlN and CrAlN-VN monolayer and periodic films were prepared by magnetron sputtering on cemented carbide YG8 and?100?monocrystalline silicon,the effect of modulation structure on the properties of periodic films is studied systematically.The phase structure,surface morphology,hardness and elastic modulus of the films were characterized by X-ray diffractometer,energy dispersive spectrometer,confocal laser scanning microscope and nanoindenter.The toughness of the film was characterized by vickers hardness tester and laser scanning confocal microscopy.The interface structure of the film was characterized by X-ray reflectance method.The result show:CrAlN/AlN periodic films have a fcc structure under different modulation structures.The hardness of the periodic film with different modulation period is always lower than CrAlN monolayer film?21.78GPa?,and the maximum value is 19.2GPa when the modulation is 27 nm.When the modulation ratio of CrAlN sublayer to AlN sublayer is between 8:1 and 2:1,the hardness fluctuates around 22 GPa,and the hardness of the periodic film reaches a maximum value of 22.86 GPa when modulation ratio is 5:1,resulting in a hardening effect.For the plastic deformation resistance(H³/E^*2),it increases first and then decreaseswith the increase ofmodulation period,and it reaches a maximum at the modulation period of 27 nm which is slightly higher than monolayer CrAlN film.When the modulation ratio of CrAlN sublayer to AlN sublayer is between 8:1 and 2:1,the H³/E^*2 value fluctuates around 0.065 GPa,and the maximum is 0.071 GPa when the modulation ratio is 5:1.This maximum value is more than CrAl Nmonolayer film by 39%.Compared with the monolayer,the toughness of the periodic film increased by 24%.The toughness of the periodic films are irregularly changed with the modulation period change,but the toughness of the periodic films are decreased due to the decrease of the modulation ratio.CrAlN/VN periodic films have a fcc structure under different modulation structures.The hardness of films increases with the decrease of modulation period,and the maximum value is 20.23 GPa when the modulation is 10 nm.With the increase of the CrAlN sublayer and VN sublayer thickness difference,the hardness of the periodic films increase,and the hardness of the periodic film reaches a maximum value of 22.08 GPa when modulation ratio is 1:4,resulting in a hardening effect.The plastic deformation resistance increases with the increase of modulation period and thickness difference of the CrAlN sublayer and VN sublayer,and its maximum value is 0.057 GPa,relative to the VN increased by 21.3%.The toughness of the periodic film is better than CrAlN only in the periodic structure which is 10 nm modulation period and 1:4 modulation ratio,relative to the CrAlN increased by 21.8% and the periodic films with the other modulation structures are lower than the monolayer films.The results of X-ray reflectivity method for the characterization of periodic films indicate: both of CrAlN/AlN periodic films with different structures of CrAlN and AlN sublayer and CrAlN/VN periodic films with the same structure CrAlN and VN sublayer exhibit good periodicity.