Preparation And The Study Of Wear Resistance Properties Of ZrNbTiMo High-entropy Alloy Films

High-entropy alloy film,as a new alloy film material,has received a lot of attention from scholars at home and abroad for its excellent properties.In this paper,ZrNbTiMo high-entropy alloy thin films were prepared using magnetron sputtering technique,and the effects of different substrate bias and sputtering power on the chemical composition,morphological structure,phase composition,mechanical properties and tribological properties of ZrNbTiMo high-entropy alloy films were investigated,and the growth mechanism and wear resistance mechanism of ZrNbTiMo thin films were discussed.The effects of not using oxidation temperature on the microstructure,mechanical properties and oxidation resistance of ZrNbTiMo high-entropy alloy films with the best combination of mechanical and tribological properties were investigated by high-temperature oxidation tests,and the oxidation laws of ZrNbTiMo films were discussed.The main studies are as follows.（1）The study of the effects of different substrate biases on the structure and properties of ZrNbTiMo films shows that with the substrate bias increasing from 0 to-100 V,the sputtering shadow effect is eliminated,the ion bombardment effect and the atomic diffusion ability are enhanced,the cross-section of ZrNbTiMo films changes from a fine fiber structure to a dense columnar structure,and the surface roughness decreases from 3.9 to 2.0 nm;the ZrNbTiMo films possess a single-phase BCC structure,the enhanced ion bombardment effect increases the strain energy of the film,and the preferential orientation of the film gradually changes from（110）to（200）;the gradual densification of the structure increases the nano-hardness of the ZrNbTiMo film from 6.8 to 14.8 GPa,and the compressive residual stress increases to-0.85 GPa;the films prepared at-100 V have the best adhesion（15.1 N）and fracture toughness(0.96 MPa×m^1/2).As the substrate bias increases to-200 V,the ion bombardment effect enhances the ion etching on the films,and the surface roughness increases to 4.1 nm.In addition,the ion bombardment effect leads to many crystal defects in the films,and the film cross-section transforms into an irregular layer microstructure;the film hardness further increases to 21.3 GPa,and the residual stress shifts to tensile stress,the adhesion decreases.The friction results show that the films deposited at low bias voltage（-100 V）possess good wear resistance(wear rate of2.05×10^-6mm³/N·m),which is attributed to the unique"inter-column sliding deformation mechanism"of the ZrNbTiMo films,the wear mechanism of the films is mainly plastic deformation with a small amount of oxidative wear characteristics.（2）The study of the effect of different sputtering powers on the structure and properties of ZrNbTiMo films shows that with the increase of power from 90 to 150W,the kinetic energy of deposited atoms increases,the diffusion ability is enhanced,and the cross-section of ZrNbTiMo films changes from a fine fiber structure to a dense columnar structure;the ZrNbTiMo films possess BCC-type nanocrystalline structure,the crystallinity of the films increases from 13.0 to 20.1%and the average grain size increases from 2.6 to 15.3 nm due to the increased diffusion ability of the deposited atoms;the"composite fracture mode"induced by the nanocrystalline structure improves the toughness of the films;the best fracture toughness(0.44MPa×m^1/2)is obtained for the film prepared at 150 W,and the film’s adhesion and compressive residual stresses are 12.2 N and-0.56 GPa,respectively.As the sputter power further increases to 210 W,the increased deposition rate limits the diffusion of the deposited atoms,the cross-section of ZrNbTiMo films changes to fine fiber structure and the crystallinity decreases to 2.4%;the residual stress of the films shifts to tensile stress,the toughness and adhesion are significantly reduced,and the hardness of the film remains almost constant（7.0±0.5 GPa）.The friction results show that the films deposited at 150 W possess good wear resistance(wear rate of 5.22×10^-7mm³/N·m),which is attributed to the nanocrystalline structure in the ZrNbTiMo films,the films’toughness is improved,the propagation of cracks is relieved during wear,the wear mechanism of the films is mainly fatigue wear with a small amount of abrasive wear characteristics.（3）ZrNbTiMo films deposited at 150 W and-100 V were selected for oxidation resistance testing,and the effects of different oxidation temperatures on the structure and properties of the film shows that with the temperature increasing from RT to600℃,oxygen atoms gradually diffuse into the ZrNbTiMo film,and the oxygen content on the film surface increases from 5.10 to 70.86 at.%,and the oxidation degree of the film increases;the film changes from a single-phase BCC structure at RT to an amorphous structure at 400℃,and finally diffraction peaks with phase characteristics of ZrO₂,Nb₂O₅,and Zr（MoO₄）₂are detected at 600℃,and the mass generation of oxides increases the surface roughness of ZrNbTiMo films from 2.10 to50.59 nm,and the film thickness expands from 1.20 to 3.13μm.After oxidation at600℃,the film section changes from a dense columnar structure to a loose and porous layered structure,which leads to a decrease in the toughness of the film and a decrease in adhesion from 12.5 to 4.6 N;the oxidation kinetic analysis shows that the oxidative activation energy（Ea）of ZrNbTiMo films is 51.6 k J/mol at Rt—600℃and the oxidation rate constant（k_o）is 6.34E-9 g²/cm⁴/s at 600℃.