In order to provide technical support and theoretical support for the application of AlxCrFeNi3Ti0.3high-entropy alloy in the tribological field，the AlxCrFeNi3Ti0.3high-entropy alloys (HEAs) were prepared by arc melting，and the effects of the Al contents on the microstructure，mechanical and tribological properties of the HEAs were investigated by X-ray diffractometer，Vickers hardness tester，friction testing machine，universal testing machine，three-dimensional profilometer，scanning electron microscope，etc.Results showed that the addition of the Al made the microstructure of the HEAs transformed from a single FCC phase to a coexistence of FCC and BCC with dendritic structure.With the increase of the Al content，the density of the HEAs decreased while the hardness，yield strength and compressive strength of the HEAs increased significantly，showing excellent comprehensive mechanical properties.Moreover，the addition of the Al significantly improved the wear resistance of the HEAs，in which the room temperature wear resistance of the Al1.2CrFeNi3Ti0.3HEA increased about 8 times compared with that of the HEA without Al.The wear mechanism of the HEAs changed from abrasive wear to oxidative wear with increasing Al content.Besides，the increase in strength and hardness as well as the formation of the hard oxide layer on the worn surface were the main reasons for the improved wear resistance of the HEAs.

Motion devices in high temperature environments suffer serious friction and wear damage，which puts forward strict requirements for their surface protective coatings.High-entropy alloys have good composition design flexibility and excellent comprehensive properties.Low friction and high wear resistant coatings can be obtained through composition regulation，thereby achieving efficient protection of high temperature service components.In order to obtain low friction and wear resistant protective coatings for moving parts servicing in high temperatures in this paper，VAlTiCr-based high-entropy alloy coatings were prepared by magnetron sputtering.The effects of different elements (Mo，W，and Si) and heat treatment temperatures (700，800，and 900 ℃) on the crystal structure and high temperature friction properties of high-entropy alloy coatings were studied.Results showed that the as-prepared VAlTiCrSi coating was amorphous，while the VAlTiCrMo and VAlTiCrW coatings exhibited BCC solid solution structure.The tribological properties of the coatings after heat treatment were tested at 700 ℃，which showed that with the increase of heat treatment temperature，the friction coefficient and wear rate of the three coatings decreased first and then increased；And after heat treatment at 800 ℃，VAlTiCrMo，VAlTiCrW and VAlTiCrSi coatings all had the best tribological properties.Oxides such as V2O5 and AlVO4 played a major role in lubrication.VAlTiCrMo coating has better comprehensive friction performance than VAlTiCrSi and VAlTiCrW coatings.The friction coefficient was as low as 0.21，and the wear rate was only 9.98×10-5mm3/(N·m).Therefore，the element regulation and heat treatment of high-entropy alloy coating could provide data reference for the research of the high-performance protective coating serving in harsh environments.

As a kind of promising candidate materials in the field of corrosion protection，the multi-component carbide coatings have low friction coefficient，low wear rate and good corrosion resistance，but there are few studies on the tribocorrosion performance.In order to promote the application of the multi-component carbide coatings in seawater environment，the (TiNbMoZrW)C coatings were prepared via reactive magnetron sputtering under various pulse bias voltages.The microstructures and the mechanical properties of the (TiNbMoZrW)C coatings were systematically characterized by X-ray diffraction，X-ray photoelectron spectroscopy，atomic force microscope，scanning electron microscope，Vickers indentation and nano-indentation experiment.In addition，the electrochemical characteristics and friction and corrosion properties of coatings in artificial seawater were analyzed.Results showed that the pressure residual stress，hardness and elastic modulus of the prepared (TiNbMoZrW)C coating showed an increasing trend when the pulse bias increased from 0 to -800 V.The (TiNbMoZrW)C coating deposited under -800 V pulse bias had the maximum hardness (25.9 GPa) and the maximum elastic modulus (365.34 GPa)，excellent crack and corrosion resistance，which exhibited the lowest wear rate in artificial seawater [1.00×10-7mm3/(N·m)] and air [2.28×10-7mm3/(N·m)].Meanwhile，the application of higher pulse bias was beneficial to improve the tribocorrosion performance of the (TiNbMoZrW)C coatings in artificial seawater.

Nonmetal doped high-entropy alloys have excellent mechanical properties，wear resistance and corrosion resistance，but there is still much room for improvement friction properties in high temperature.It is expected to achieve low friction through utilizing the characteristics of high-entropy alloys，when they are applied to high temperature working moving parts.In this work，(VAlTiCrW)Oxhigh-entropy alloy coatings with various oxygen content were prepared on the substrate surface by magnetron sputtering.The microstructure and tribological properties of the coating were evaluated by scanning electron microscope，atomic force microscope，X-ray diffractometer，high temperature friction testing machine，surface profiler，3D optical profiler and Raman spectroscopy.Results showed that with the increase of oxygen content，the coating structure gradually changed from BCC to indefinite amorphous structure，the hardness of the coating increased from 3.3 GPa to 11.9 GPa，and the elastic modulus increased from 97.92G Pa to 181.70 GPa.The average friction coefficient of the coating decreased from 0.49 to 0.39 at 700 ℃，but the wear rateincreased from 1.97× 10-5mm3/(N·m) to 6.41×10-4mm3/(N·m).Moreover，lowfriction coefficientresultedfrom the fact that oxygen doped coatings were more likely to form V2O5with lubricating effect at high temperatures，and correspondingly the wear rate of the coating increases due to the softening effect of V2O5.

The concept of high-entropy alloy not only greatly enriches the metal material system，but also breaks the design routine of traditional ceramic material.In recent years，people are gradually extending the design concept of multi-principal and high-entropy to ceramic materials，and a series of multi-principal high-entropy ceramics have been fabricated.Thanks to its unique structure and “four effects”similar to high-entropy alloy，high-entropy ceramics exhibit a series of excellent mechanical，thermal and tribological properties.Based on the preparation methods，structural characteristics and properties，this article mainly introduced the research progress of high-entropy oxide，carbide，nitride ceramics and other high-entropy carbonitrides，borides，silicides and sulfides at home and abroad，and analyzed the specific structures and properties of those high-entropy ceramics.Finally，the development prospect of the high-entropy ceramic was also prospected.

Preparing various types of coatings to strengthen the surface of materials is a significant technique to increase the materials' service performance，and the addition of different content of hard phase is conducive to further improve the properties of coatings.The Fe50Mn30Cr10Co10 high-entropy alloy coating with different VC content were prepared through selective laser cladding process，and the effects of VC content on the microstructure，the phase structure，the hardness and the creep properties of the coatings were researched by scanning electron microscope，X-ray diffractometer，nano indentation instrument，etc.Results showed that the coating structure was obviously refined with the increase of VC content.There was no effect on the phase structure of the coating，because of VC being dissolved in FCC lattice.The hardness of the coating increased，owing to the increase of solid solution strengthening effect.Particularly，with the increase of VC content，the creep value of the coating decreased，which was very beneficial to improve the creep performance of the coating material.This provided an important basis for strengthening the properties of the coating of high-entropy alloy by adding VC hard phase.

For studying the effect of nitriding treatment on the microstructure and wear properties of HVOF sprayed Al1-xCoCrFeNiTix(x＝0，0.125，0.250) high-entropy alloy coatings，the HVOF technology was employed to prepare Al1-xCoCrFeNiTix(x＝0，0.125，0.250) highentropy alloy coating on 35CrMo steel substrate，which were further nitrided.The effects of nitriding treatment on the microstructure and wear properties of Al1-xCoCrFeNiTix(x＝0，0.125，0.250) high-entropy alloy coating prepared by HVOF were studied via characterization methods such as SEM，XRD，3D white light interferometer and EDS.Results showed that the high-entropy alloy coating of Al1-xCoCrFeNiTix(x＝0，0.125，0.250) after nitriding treatment had a dense microstructure with a typical thermal spray coating-like structure.The coating thickness was about 300～350 μm，the nitriding layer thickness was about 10 μm，and the nitriding layer phase structure was FCC phase and AlN，CrN and other nitriding phases.Meanwhile，the microhardness of the nitriding layer was 981 HV2N(x＝0)，1 090 HV2N(x＝0.125) and 1 194 HV2N(x＝0.250)，respectively，which was significantly improved compared with the microhardness of 479 HV2N(x＝0)，506 HV2N(x＝0.125) and 548 HV2N(x＝0.250) of the unnitrided high-entropy alloy coating.With the increase of Ti content，the wear resistance of the nitriding layer increased，and Al0.750CoCrFeNiTi0.250nitriding layer possessed the best wear resistance [(2.17×10-6mm3/(N·m)].Besides，the wear failure mechanism of Al1-xCoCrFeNiTix(x＝0，0.125，0.250) nitriding layer was mainly abrasive wear，oxidation wear and adhesive wear.