Preparation,Microstructure And Properties Of CrNbTiMoZr High-entropy Alloy Films

As a branch of high-entropy alloys,high-entropy alloy films has excellent performance.Compared with high-entropy alloy bulk materials,thin films have economic effect and‘rapid quenching'effect,and the‘rapid quenching'effect makes it easier to form simple solid solutions.Therefore,it is a great significance to conduct in-depth research on high-entropy alloy films.In this paper,we firstly designed a new CrNbTiMoZr high-entropy alloy system and prepared CrNbTiMoZr films by DC magnetron sputtering,and studied the composition,morphology,structure and properties of CrNbTiMoZr films under different bias voltages.Secondly,(CrNbTiMoZr)C films were designed and prepared in order to address the shortcomings of CrNbTiMoZr films,such as high friction coefficient and severe adhesive wear.The mechanical properties and tribological properties of(CrNbTiMoZr)C films under different bias voltages were systematically investigated.Meanwhile,the roles of carbon in improving the mechanical and tribological properties of(CrNbTiMoZr)C films were analyzed.The specific results of the study are as follows:(1)The study on the structure and properties of CrNbTiMoZr films shows that the films deposited at 0 V and-150 V exhibit amorphous and BCC nanocrystalline composite structures,while the films deposited at other bias voltages display amorphous structures.As the substrate bias voltage increases,the hardness of the films increases first and then decreases.When the bias voltage is-150V,the hardness reaches its maximum value,about9.7 GPa.The change of the bias voltage has no effect on the friction coefficient of films,and the friction coefficient of all the films is about 0.5.However,the wear tracks of films gradually become wide and deep with the increase of the bias voltage.When the bias voltage is-150 V,these films occur wear-out failure.Furthermore,the friction mechanism of all CrNbTiMoZr films is adhesive wear.(2)The study on the structure and properties of(CrNbTiMoZr)C films shows that the(CrNbTiMoZr)C films without bias voltage have an amorphous structure,while the carbide films under different bias voltages exhibit an FCC structure with(111)preferred orientation.As the bias voltage increases from 0 V to-200 V,the residual stress increases from-1.13 GPa to-2.22 GPa,and the hardness increases from 7.6 GPa to 17.4 GPa.Under the same bias,the hardness of the(CrNbTiMoZr)C film is nearly twice that of the CrNbTiMoZr film.In addition,the friction coefficient of all(CrNbTiMoZr)C films is about 0.35,while the friction coefficient of CrNbTiMoZr films is 0.5.At the same time,the(CrNbTiMoZr)C film deposited at-200 V has the lowest wear rate,about 1.18×10^-6mm³/N·m,which is much lower than the traditional binary carbide film.The addition of carbon changes the wear mechanism of the films from adhesive wear to abrasive wear.