Microstructure And Properties Of (AlSiTiVNbCrBx)N High Entropy Alloy Film By Magnetron Sputtering

In recent years,the development of hard films has attracted much attention.However,it has been restricted due to their low hardness,poor high-temperature stability,poor corrosion resistance and poor wear resistance.High entropy alloys?HEA?with special structure and excellent properties have been attracted much attention.The preparation of HEA films is expected to obtain film materials with excellent comprehensive properties,which provides a new method for the design of hard films.In this paper,AlSiTiVNbCr high entropy alloy was prepared by vacuum arc melting technology,and processed into a target.Then the alloy target and B target were designed by tooling to prepare the composite targets with different B content.?AlSiTiVNbCr Bx?N HEA film was prepared on Si and M2 high-speed steel by reactive magnetron sputtering technology.The effects of B content in the composite targets,sputtering power,negative bias,and substrate temperature on the microhardness and adhesion of the film were studied.The effects of B content in the composite targets and nitrogen partial pressure on the microstructure,surface morphology and mechanical properties of the film were analyzed.Furthermore,the adhesion and wear properties of the film with optimized design of transition layer were evaluated.The results are as follows:AlSiTiVNbCr targets showed FCC,BCC and Laves phase structures.There were a large number of slab-like and dendritic precipitates.Except for aluminum,other alloy elements were close to the isotonic ratio in the HEA film.Orthogonal experiments showed that the target boron content,sputtering power and negative bias had a positive correlation with the film hardness,and the substrate temperature was opposite.The optimized preparation process of the film was as follows:the number of boron targets was 4,the sputtering power was 200W,the negative bias voltage was 200V,and the substrate temperature was at 200?.The corresponding film microhardness and elastic modulus were 60GPa and 68N,respectively.The high-entropy alloy film tended to be an amorphous structure with the addition of boron element.Due to the refinement of the crystal grains,the film became compact and flat,which resulted in an improvement of the hardness and elastic modulus.The growth rates of the films were affected by the boron target.The structure of the films changed from amorphous to single-phase FCC structure by increased nitrogen partial pressure.Affected by the nitrogen partial pressure,the bombardment energy of sputtering ions was weakened,which increased the grain size,porosity and roughness.The existence of voids resulted in a reduction of the resistance to deformation under load of the films,and the comprehensive mechanical properties of the film were also reduced under a large nitrogen partial pressure.Therefore,the growth rate of the film at a nitrogen-argon ratio of 4:5 was nearly doubled compared with the nitrogen-argon ratio of 1:5.The?AlSiTiVNbCr B₄?N film had the best performance at a nitrogen-argon ratio of 2:5.Thermal shock experiments showed that the?AlSiTiVNbCr B₄?N film with Cr/CrN as the transition layer had the best bonding force on the M2 high-speed steel substrate.The?AlSiTiVNbCr B₄?N film with Si₃N₄had better wear resistance during grinding,and there was no obvious adhesion phenomenon.The friction coefficient was 0.58,which was lower than that of the substrate material was 0.78.The wear performance of the film in cutting fluid and seawater environment was better than that of the traditional TiN and CrN hard film.