Preparation Of CrMnFeCoMoW High Entropy Alloys And Al-based Composite Coatings By Mechanical Alloying

As a new type of alloy,high-entropy alloy has attracted great interest from researchers due to its excellent properties and great application potential,and is called one of the three future materials.Titanium alloy has the characteristics of high specific strength,good corrosion resistance,light weight,good biocompatibility and so on,has been widely used in the field of aerospace and medical devices,but there are also some defects of titanium alloy,such as easy to be oxidized under high temperature,poor wear resistance and so on,seriously restricted the application of titanium alloy.In this paper,a composite coating of high entropy alloy on the surface of TC4 titanium alloy was prepared by combining high entropy alloy with mechanical alloying method.aiming at making up for the deficiency of high-temperature oxidation property of titanium alloy with the excellent high-entropy alloy at high temperature.CrMnFeCoMoW high-entropy alloy powders were prepared by mechanical alloying of Cr,Mn,Fe,Co,Mo and W powders at 1:1 atomic ratio.The effect of different milling time on the morphology and phase structure of powder particles was studied.After 80 h ball milling,the alloy powder size to 5 μm.XRD results show that the phase structure is BCC+FCC.Al element was selected as the adhesive to prepare the prepared CrMnFeCoMoW high entropy alloy powder into the composite coating of al-crmnfecomow high entropy alloy on the TC4 Substrate.The effects of Al content and milling time on the preparation,microstructure and phase composition of the coatings were investigated.Furthermore,the adhesion,microhardness and high temperature oxidation of the composite coatings were tested under the optimum parameters,And the oxidation products were deeply analyzed to explore the mechanism of high temperature protection of the coatings.Compared with traditional Al-Si and Al-Cr coatings,Al-CrMnFeCoMoW composite coatings exhibit better high temperature oxidation resistance.Aiming at the large plastic deformation and internal stress of mechanical alloying coating,the coating samples were annealed at different temperature and time.The influences of different annealing temperatures and different annealing time on the composition,structure,composition and properties of the coating phase were investigated.The results of microhardness and cyclic oxidation test showed that the hardness of the coatings increased significantly after annealing,and the samples had the best high temperature oxidation resistance after holding for 12 hours at 400℃.