Microstructure And Properties Of CrNiAlCoMoB_x High-Entropy Alloy Coating Prepared By Laser Cladding

High-entropy alloys have lots of advantages such as high strength,excellent corrosion resistance,high wear resistance,etc.These advantages have arisen domestic and international scholars’attention and enthusiastic exploration.Al_xCoCrNiMo high-entropy alloy coating was prepared by other scholars through the method of laser cladding,and its hardness was high at room and high temperature.But macroscopic morphology of the coating was bad and the problem of crack was serious.This paper was to improve the problem by adding different content of B elements.CrNiAlCoMoB_x high-entropy alloy coatings were prepared by laser cladding on45#steel with mixed pure mental powders.Different effects of the laser cladding processing parameters on coating were studied and the optimum parameters were found.Then a series of CrNiAlCoMoB_x high-entropy alloy coatings were prepared by suitable parameters.The microstructure,dilute rate,phase structure and hardness of the coating were separately analyzed by OM,SEM,stereomicroscope,EDS,XRD and microhardness tester.Excellent performances of friction,corrosion resistance and high-temperature softening resistance of CrNiAlCoMoB_0.5.5 coating were tested.The result shows that with the constant laser power,as the increasing of scanning speed,the microstructure of coatings are denser,the grains and the dilute rates are smaller.With the constant scanning speed,as the increasing of laser power,the microstructure and the dilute rates of coatings are larger.All coatings of the CrNiAlCoMoB_x high-entropy alloy share the similar properties--simple solid solution,dendrite and net-eutectic structure.The CrNiAlCoMoB_0.5.5 high-entropy alloy coating,which was prepared with the optimized parameters,is smooth.The CrNiAlCoMoB_x coating is hard and the average hardness is over 700 HV_0.2.The CrNiAlCoMoB_0.5high-entropy alloy coating is hardest which hardness is 900 HV_0.2.The friction performance of this coating is better than H13 steel.Moreover,this coating shows greatly corrosion resistance as 304 stainless steel in the solution,which is composed of1 M NaCl,1 M H₂SO₄ and 1 M NaOH.After 4h annealing at 300℃and 550℃respectively,the microstructure and phases structure of the CrNi Al CoMoB_0.5high-entropy alloy coating do not change and when the annealing temperature is over800℃,the sticks phase precipitate in the interdendritic.The hardness stay unchanged all the time.The coating has good resistance to softening at elevated temperature.