Preparation And Properties Of Laser Cladding Alalloy+rare Earth Oxide Composite Coatings On Magnesium Alloys

Magnesium alloy has been widely used in industrial production due to its characteristics of low density,good heat dissipation,high specific strength,high specific stiffness and large elastic modulus.However,the low hardness,wear resistance and corrosion resistance of magnesium alloy restrict its wide application.Laser cladding technology has been widely used in the surface modification of magnesium alloys due to its controllable energy and fast heating and cooling speed.In this paper,aluminum alloy and rare earth oxide coating was prepared by laser cladding technology on magnesium alloy surface.And the effects of different contents of rare earth oxides and laser processing parameters on the surface microstructure and properties of magnesium alloys were investigated.The microstructure and properties of the materials were analyzed by X-ray diffractometer,scanning electron microscope,energy dispersive spectrometer,Vickers hardness tester,friction and wear tester and electrochemical workstation.The specific research results are as follows:(1)In Al-Si+x Y₂O₃(x=0%,2.5%,5%,7.5%,10%)coating,it was found that the coatings were composed of Mg₁₇Al₁₂,Mg₂Al₃,Mg₂Si and?-Mg,and Al₄Mg Y was detected by adding Y₂O₃.With the increase of Y₂O₃content,the grain refinement and surface properties of the coating increase first and then decrease,and the peak value was reached when the content of Y₂O₃was 7.5wt.%:The average hardness of the coating(280.5HV)is 3.6 times that of the matrix,the wear resistance is 73.23%higher than that of the matrix,and the self-corrosion current density is two orders of magnitude lower than that of the matrix.When the content of Y₂O₃is 7.5wt.%and the scanning speed is 400mm/min,the surface properties of the coating increase gradually with the decrease of laser power(1.1k W-1.4k W).The coating with 1.1k W laser power has the best surface performance,with hardness 3.7 times that of the matrix,wear resistance 77.15%higher than that of the matrix,and self-corrosion current density three orders of magnitude lower than that of the matrix.When the content of Y₂O₃is 7.5wt.%and the laser power is 1.3k W,with the increase of scanning speed,wear and corrosion resistance of the coating becomes stronger first and then weaker,and the coating with scanning speed of 400mm/min has the best wear resistance,which increases 73.32%compared with the matrix.The coating with scanning speed of 500mm/min has the best corrosion resistance.(2)In Al-Cu+x Y₂O₃(x=0%,1.5%,2.5%,5%,7.5%,10%)coating,the results show that with the increase of Y₂O₃content,the coating grain becomes fine first and then coarser,and reaches the maximum fine grain when the content of Y₂O₃is 2.5wt.%,and the surface property is the best.At this time,the average hardness(208.3HV)is 2.6 times that of the matrix,the wear resistance increases by 68.36%,and the self-corrosion current density decreases by three orders of magnitude.When the content of Y₂O₃is 2.5wt.%,it is found that the hardness and wear resistance of the coating with lower energy density are the highest,the hardness is 3-4 times of the matrix,and the wear resistance is increased by more than 70%.The corrosion resistance of the coating increases and then decreases with the decrease of energy density.