Formation Mechanism And Properties Of (AlSiTiVCrNb)N HEAs Films With High Hardness

High entropy alloys(HEAs)with excellent performance have attracted wide attention in the field of manufacturing and processing.As a new high-performance alloy coating,it often presents excellent comprehensive aesthetic performance and has high research value and broad application prospects.The elements of N or C are added to form high entropy nitrides and high entropy carbides respectively,which can enhance the hardness,thermal stability,corrosion resistance and wear resistance of the coatings.By regulating process parameters(sputtering power,negative bias,substrate temperature and gas flow),as well as multi-layer structure,(AlSiTiVCrNb)N and(AlSiTiVCrNb)CN films with high hardness and good binding ability can be deposited on Si and high-speed steel substrates,which provides experimental support for applications of high entropy alloys and their nitride films in many fields.The structure of the HEAs films were analyzed by X-ray diffraction and transmission electron microscopy.The surface particle size,fracture morphology,film thickness and wear morphology was observed by the scanning electron microscopy.The element distribution of the films was analyzed by an energy dispersive spectrometer.The surface roughness and 3D image of abrasion was obtained by the white light interferometer.The hardness and elastic modulus of the films was measured by the nanoindentation instrument.The friction coefficient and wear rate of the films were tested and analyzed by the tribological tester.The corrosion performance of the samples was tested by the potentiodynamic scanning technology;The adhesion of the films was tested by the scratch tester.The results are as follows:It was found by orthogonal experiment that the(AlSiTiVCrNb)N films prepared by the reactive magnetically controlled sputtering are mainly composed of FCC solid-soluble nanocrystalline,which have a small number of amorphous phases and a diffraction peak structure with composite membrane characteristics.The deposition of different elements in the films corresponds to the content of each element in the target material.Part of the films near the Si substrate has no obvious growth direction,and the particles are small and dense.Part of the films far away from the substrate can observe a significant column growth trend perpendicular to the direction of the silicon.The thickness of the films fluctuates with the process,and the power plays a decisive role in the films thickness control.The mechanical property is affected by the process parameters:temperature>negative bias>power.The mechanical property increases with the increase of temperature and negative bias,and the hardness is up to 37.24 GPa,which is about three times the AlSiTiVCrNb target.With an increase of carbon target power,the deposition rate,stress,hardness and adhesion of(AlSiTiVCrNb)CN films decrease.The wear resistance of the films is the best as the carbon target power is 150 W.With an increase of substrate temperature or negative bias,the crystallization of the(AlSiTiVNbCr)CN films decreases,and the surface roughness increases.The films with substrate temperature of 450℃ have the highest hardness,and the film with the negative bias voltage of 250 V has the best comprehensive performance.The(AlSiTiVCrNb)N and(AlSiTiVCrNb)CN films deposited using the best process have the hardness of 40.87 GPa and 37.31 GPa,respectively.In addition,it is found that the introduction of carbon can inhibit the preferred orientation growth of columnar crystals.Although the thickness of the films prepared by continuous sputtering for a long time increases,the surface particles have coarsened and hardness suddenly dropped,and the excessive stress easily leads to the peeling of the films from the substrates.To optimize the properties of the films and reduce the stress in the films,the multi-layer films are prepared with(AlSiTiVCrNb)N and(AlSiTiVCrNb)CN as a modulation period.The particle growth of the multi-layer films is controlled by the way of interval stacking.The particles on the multilayer films are fine and evenly distributed,and the growth rate is improved.As the modulation period is large,the interface of the multi-layer films is clear,and the difference of hardness between the layers is obvious,which leads to brittle fracture failure at the boundary of wear marks.As the modulation period is 7.67 nm,the hardness of the film is up to 47.43 GPa,and the bonding force is increased over 10 N.As the modulation period is less than 10 nm,the oxidation products are found on the films by thermal shock experiment,but there was no obvious peeling or bulging phenomenon.