Preparation And Performance Study Of Nitride Periodic Structure Multilayer Films

With the development of advanced machining technology and intelligent manufacturing industry,it is not only required that cutting tools have high hardness,wear resistance,and stable chemical properties,but also meet the working conditions of workpieces in harsh environments.As a commonly used protective material,coatings play an important role in improving the wear resistance and lifespan of cutting tools.Transition metal nitride periodic structure multilayer films have advantages such as high melting point,high hardness,good corrosion resistance,and oxidation resistance.They are often used as surface strengthening and protection materials for workpieces,such as cutting tools,to meet the requirements of cutting tool materials under different usage conditions,and have important research value.In this thesis,nitride periodic multilayer films were prepared by reactive Magnetron sputtering,and the properties of the films were studied.Firstly,investigate the effect of reaction gas flow rate on the composition,structure,and performance of TiN,Cr O_xN_yand(CrVTaTiW)N_x monolayers.Then,according to the research results of single layer films,the periodic structure multilayers are studied to explore the effects of process parameters such as target power,gas flow,modulation layer thickness and annealing temperature on the composition,structure,mechanical properties and thermal stability of periodic structure multilayers.The main research findings are as follows:The research results on single-layer films indicate that for TiN thin films,when the nitrogen flow rate is greater than 1 sccm,the films exhibit a face centered cubic structure.As the nitrogen flow rate increases,the preferred orientation of the crystal plane changes from(200)to(111),and the grain size decreases.For Cr O_xN_y thin films,the thin films prepared under pure argon atmosphere exist in the form of Cr O_x.As the nitrogen flow rate increases,the thin film coexists in the form of Cr O_x and Cr N.For the(CrVTaTiW)N_x thin film,the CrVTaTiW high entropy alloy film exhibits a body centered cubic structure,while the(CrVTaTiW)N_x thin film exhibits a face centered cubic structure.As the nitrogen flow rate increases,when the nitrogen flow rate is 30 sccm,the preferred orientation of the crystal plane changes from(200)to(111),and the hardness also increases,reaching a maximum of 38 GPa.After vacuum low-temperature annealing at 300℃,the hardness of the sample increased from21 GPa to 25 GPa.The research results on TiN/CrO_xN_y periodic multilayer films show that all multilayer samples exhibit a face centered cubic structure and grow preferentially along the TiN(200)crystal plane.When Ti pre coating is present,the crystallinity of the sample is not affected by the substrate,but the introduction of nitrogen reduces the crystallinity and thermal stability of the film.The TEM results indicate that under the action of the template layer,some of the deposited Cr O_xN_y amorphous layers are strengthened and crystallized into metastable crystals.The multilayer film exhibits a coherent epitaxial growth structure,and dislocations are generated at the interface between the modulation layers to improve hardness.The maximum hardness of the sample prepared in pure argon atmosphere is 29 GPa.The research results of TiN/(CrVTaTiW)N_x periodic structure multilayer films show that all multilayer samples have a face centered cubic structure and grow in a(111)preferred crystal orientation.As the thickness of the(CrVTaTiW)N_x layer increases,the grain size decreases.The TEM results showed that both modulation layers underwent co lattice epitaxial growth during the deposition process,resulting in lattice mismatch and the generation of dislocations at the interface,which improved the hardness of the thin film.When TiN was used as the template layer,the sample prepared had a higher hardness of up to 25 GPa.After vacuum annealing at 300℃,the nitrogen element in(CrVTaTiW)N_x is more stably distributed and forms a more ordered and compact crystal structure,thereby increasing the hardness of the sample to 29 GPa.