Experimental Study On Of Laser Cladding Ti_0.8CoCrFeNi High-Entropy Alloy Composite Coating On TC21 Titanium Alloy

Titanium alloys have many good and excellent properties,especially in terms of mechanical and physical and chemical properties.Titanium alloys are widely applid in important fields such as aerospace manufacturing and biomedicine.However,due to their low hardness and bad wear resistance,they limit their service under extreme conditions.High-entropy alloys have high-entropy effects and mostly exist in simple solid solution structures,and have special physical and chemical properties and comprehensive mechanical properties in micro and macro.Therefore,using laser cladding technology to prepare Ti_0.8Co Cr Fe Ni high-entropy alloy coatings,which provides a certain reference for the study of TC21 titanium alloy surface modification.In this paper,Ti_0.8CoCrFeNiAl_x,Ti_0.8CoCrFeNiAl_x+xTiN high entropy alloy composite coatings were prepared on TC21 titanium alloy surface by laser cladding technology.The microstructure and phase composition of the cladding layer were analyzed by X-ray diffractometer,electron probe and scanning electron microscope.Finally,the wear resistance of the cladding layer was tested by CFT-I material surface comprehensive performance tester to explore the influence of laser processing parameters on the macro morphology,forming quality and microstructure of the cladding layer.Under the appropriate laser processing parameters,the affect of Al content change on the microstructure and properties of Ti_0.8CoCrFeNiAl_x high entropy alloy layer was explored The influences of Ti N content change on the microstructure and properties of Ti_0.8CoCrFeNiAl_x+xTiN high entropy alloy composite coating was investigated.The experimental data of the influence of laser processing parameters on the macro morphology,forming quality and microstructure of the cladding layer show that the convection and disturbance of the molten pool caused by the scanning speed and laser power have a very important influence on the forming of the cladding layer.At the same scanning speed,As the laser power increases,the dilution ratio of the cladding layer changes significantly,showing an upward trend.The effect of laser power is dominant.When the laser processing parameters are1000W and 6mm/s,the cladding layer has good appearance,no obvious cracks and holes,relatively appropriate dilution ratio and metallurgical bonding with Titanium alloy.The experimental data of Ti_0.8CoCrFeNiAl_x high-entropy alloy coating show that when the Al element content is more than 0.5,Al atoms are dissolved in the gap of the FCC1 phase solid solution or replaced with atoms with a smaller radius,which produced Lattice distortion,FCC1phase transforms into FCC2 phase;when the Al content is 0.5,the cladding layer has the lowest microhardness,and the cladding layer has lower wear resistance,which is about 2.82 times that of the TC21;when the Al content is 1.0,the microhardness of the coating is the highest,and the wear resistance of the coating is the best,which is about 5.72 times that of the TC21.The experimental data of the Ti_0.8CoCrFeNiAlx+xTiN high-entropy alloy composite coating group show that after adding Ti N,the cladding layer generates in-situ Ti N phase embedded in the dendritic and interdendritic structures.The hardness of the coating with 8%Ti N is the highest,which is 1.23 times of the cladding layer without Ti N.Ti N has a significant effect on the improvement of the wear resistance of the coating.When the content of Ti N is6%,the wear resistance is high,which is about 2.92 times of the sample without Ti N,and it has good comprehensive mechanical properties.