The Microstructure And Properties Of AlCoCrFeNiTi High-entropy Alloys Coating By Laser Cladding

High-Entropy Alloys(HEAs)break the bottleneck stage of design strategy for conventional alloy,which is based on one or two primary components and other minor elements to tailor the microstructure and properties and have excellent physical,chemical and mechanical properties.Laser cladding is effective mean of remanufactured repairing to achieve good metallurgical bond between the powder and the substrate,and maintain excellent properties of the coating materials.In term of multiple performance requirements of surface coatings remanufacturing such as mold and other key components need high corrosion resistance,wear resistance and other performance requirements,coatings material and repairing methods need to be improved.Based on excellent properties of HEAs,this paper used laser cladding technology to fabricate AlCoCrFeNiTi High-Entropy Alloy coatings(HEACs),and phase evolution,microstructure of AlCoCrFeNiTi HEAs during mechanical alloying and laser cladding processes under different parameters were intensively investigated,as well as mechanical properties and microstructure of HEACs after laser cladding,the main contents are as follows:(1)The alloying behavior,phase structure and microstructure of AlCoCrFeNiTi HEAs powders during mechanical alloying process were investigated.The results showed that alloying sequence of AlCoCrFeNiTi HEA powder related to melting points of alloying elements included in powders,when the melting point exhibited lower,the alloy more easily alloyed,and the final milling coating powders exhibited simple body centered cubic(BCC)phase and mean granular size of 4 ?m,and contained plenty of flaked nanoparticles.(2)The effects on microstructure and properties of single-bead AlCoCrFeNiTi HEACs under different laser cladding parameters were investigated,with heat input of laser power increasing,the phase of coating turned supersaturated BCC solid solution phase into stable BCC phase and secondary FCC phase.Controlling other parameters constant,as the laser power increased,dilution rate of AlCoCrFeNiTi HEACs increased,the internal grain coarsened and grew.With cladding speed increased,dilution rate of the coating tended to decrease and the coating cool time shortened,the internal organization of the coating tended dense and grain refinement.Considering the effect of both parameters,the best single-bead laser cladding process parameters were 900 W of laser power,360 mm / min of cladding speed.(3)The microstructure,phase composition and elements distribution of multi-bead AlCoCrFeNiTi HEACs under optimum parameters were investigated,the analysis showed: AlCoCrFeNiTi HEACs comprised disordered BCC1 phase,ordered BCC2 phase and TiC reinforcement phase,BCC2 ordered phase had rich Al-Ni-Ti phase,disordered BCC phase had Fe-Cr phase,widmanstatten precipitate was surrounded in BCC1 phase,where the typical spinodal breakdown structure could be observed.(4)Hardness,tensile strength,wear resistance and other properties of AlCoCrFeNiTi HEACs were investigated,hardness Variation,fracture mechanism and sliding wear behavior of the coating under different coating parameters were investigated.The results showed that the maximum hardness of AlCoCrFeNiTi HEACs is 1069 V,about five times of the hardness of H13 steel;as the laser power increased,tensile property decreased together,fracture mechanism of AlCoCrFeNiTi HEACs was mainly comprehensive effects of thermal laser cladding injury,brittle fracture and ductile fracture;AlCoCrFeNiTi HEACs can significantly improve wear resistance of substrate,the best wear resistance of the coating were prepared at 900 W laser power,which was about 5.7 times of the substrate,the main wear mechanism of the coating was adhesive wear and oxidation wear,and the wear mechanism of H13 die steel was abrasive wear and oxidation wear.