Investigation On The Structure,Mechanical,Tribological Properties And Corrosion Resistance Of High-entropy (NbMoTaW)N Films

Transition metal nitrides（TMNs）are widely used as protective coating materials due to their good mechanical properties,corrosion resistance and high chemical inertness.However,with the rapid development of modern industry,multi-factor coupling conditions are becoming more and more common,and the integration of mechanical equipment is increasing.In order to effectively improve the reliability of mechanical components,there is an urgent need to further optimize the comprehensive performance of TMNs for complex service environments.In recent years,the high-entropy materials due to high-entropy effect caused by their multi-component properties has shown better performance than that of conventional materials.Even so,the endogenous factors that improve the performance of high-entropy nitrides（HENs）relative to conventional binary and ternary nitrides deserve in-depth investigation.In addition,it is of practical significance to systematically investigate the influence laws of deposition processes（such as gas flow rate and substrate bias）on the growth,structure and properties of HENs films to achieve optimization of properties.To address these problems,this paper prepared binary Nb N,ternary Nb Mo N and high-entropy（NbMoTaW）N films using reactive magnetron sputtering technology,and systematically compared the differences in mechanical properties,tribological properties and corrosion resistance behavior of the three nitride films,revealing the reasons for the higher hardness and greater resistance to wear and corrosion of（NbMoTaW）N high-entropy nitride films compared with the conventional binary Nb N and ternary Nb Mo N films.On this basis,the mechanical and tribological properties of high-entropy（NbMoTaW）N films were further optimized by tuning the nitrogen content and substrate bias voltage.Investigation on the mechanical,tribological properties,and corrosion resistance of Nb N,Nb Mo N,and high-entropy（NbMoTaW）N films.In this work,we grew binary Nb N,ternary Nb Mo N and high-entropy（NbMoTaW）N films with（111）preferred orientation.Among them,the high-entropy（NbMoTaW）N film exhibited the highest hardness of 23.5±1.4 GPa.By combining the analysis with the theoretical calculations,it can be attributed to the high structural stability and increased elastic constants and elastic moduli when high-entropy nitride is obtained and compared to binary Nb N and ternary Nb Mo N films.（NbMoTaW）N film also exhibited the best tribological properties due to the highest H/E,together with the formation of Mo O₃ and WO₃ self-lubricating phases at the friction interface.Moreover,the film exhibited the best corrosion resistance due to the slow diffusion of Cl^-due to the lattice distortion induced by the high-entropy structure and the structural stability induced by the high-entropy effect.This work demonstrates that high-entropy TMN film constructed by introducing multiple components can simultaneously achieve higher hardness,wear resistance and corrosion resistance,and are expected to be a new generation of protective coating materials.Investigation on the growth,structure,mechanical and tribological properties of high-entropy（NbMoTaW）N_x films.Based on the first part of investigation,we systematically investigated the effect of the film deposition process on the structure of high-entropy（NbMoTaW）N films by varying the nitrogen content and substrate bias voltage,with a view to optimizing their mechanical and tribological properties.First,we prepared four（NbMoTaW）N_x（x=0,0.59,0.80 and 0.95）films with different nitrogen contents at different nitrogen flow rates.The hardness of the films gradually increases with increasing nitrogen content and reaches a maximum at x=0.80（23.2±2.1 GPa）,which is attributed to an increase in the number of strong Me-N（metal-nitrogen）bonds in the films and the decrease in VEC.The hardness value of（NbMoTaW）N_0.95 film decreased to 19.1±0.9 GPa as the nitrogen content continued to increase.Theoretical calculations show that the（NbMoTaW）N_0.80 structure has a greater degree of lattice distortion,while the presence of appropriate N ion vacancies can peg dislocations,resulting in（NbMoTaW）N_0.80 film showing higher hardness than（NbMoTaW）N_0.95.Also,the（NbMoTaW）N_0.80 film exhibited the lowest wear rate(2.63×10^-6 mm³·N^-1·m^-1)due to having the largest H/E and H³/E² values.Next,we tuned the substrate bias voltage（0,-120,-240,-360,-480 and-600 V）based on the best performing（NbMoTaW）N_0.80 film growth conditions.It is found that the hardness of the film reached maximum value（27.1±1.1 GPa）when the absolute value of the substrate bias was increased to 480 V,which is attributed to the maximum compressive stress value,the dense columnar structure and the fine grain reinforcement of the-480V film.In addition,the wear resistance of the films was significantly improved after applying bias voltage,and the-480 V sample had the lowest wear rate(7.95×10^-7mm³·N^-1·m^-1).