Research Of Laser Cladding High Entropy Alloys Coatings On Cr12MoV Die Steel Surface

Cr12MoV steel has the advantages of small deformation after heat treatment,high wear resistance,large bearing capacity,etc.,and is widely used in industrial fields.However,under the working conditions,the high pressure and friction force cause the surface to produce severe wear,and the wear resistance needs to be improved.In this paper,Ni based ceramic composite coating and high entropy alloys coating with good morphology and uniform structure were prepared on Cr12MoV steel surface by laser cladding technology.The microstructure of the coating and the substrate were analyzed and tested by scanning electron microscopy,X-ray diffractometer,Vickers hardness tester and friction and wear testing machine.This study not only repaired the worn surface of Cr12MoV,but also broadened the theoretical scope and practical application of high-entropy alloys in the research field of laser cladding,and further verified the unique advantages of high entropy alloys compared with traditional Ni-based alloys.（1）Laser cladding Ni60+10%WC coating.The coating phase consists of Cr-Fe-Ni,γ-（Fe,Ni）,Cr₂₃C₆,Cr₇C₃and W₂C.The hardness of the coating increases by 128%～133%,the friction coefficient decreases by 28.89%～55.56%,and the wear volume decreases by68.95%～79.45%.Among them,the coating with good hardness and wear resistance can be obtained under the parameters of 1500W laser power and 200mm/min scanning speed.（2）Numerical simulation of laser cladding process of Al₂CrFeNiMo high entropy alloys coating.The laser heat source is a double ellipsoid heat source.The results show that the depth and width of the molten pool are 1.82mm and 2.46mm respectively at 1600W laser power and180mm/min scanning speed.In addition,the temperature variation trend of cladding layer is the same in the transverse direction.In the longitudinal direction,only the three tracking points close to the coating have significant temperature changes.（3）In addition,the thermal cycle curve was analyzed according to the simulation results,and the temperature variation trend of cladding layer was the same in the transverse direction.In the longitudinal direction,only the three tracking points close to the coating have significant temperature changes,and the thermal influence range of laser cladding is relatively small.（3）Laser cladding Al₂CrFeNiMo high entropy alloys coating.The coating phase is BCC phase,the microstructure of cladding zone is equiaxed crystal,and the microstructure of binding zone is columnar crystal.The hardness of the coating increases first and then decreases.The average hardness is 2.27～2.50 times that of the substrate,the friction coefficient（0.23～0.38）decreases by26%～41%compared with that of the substrate（0.45）,and the wear volume decreases by77.17%～91.32%.Among them,the laser power of 1600W,scanning speed 180mm/min parameters can obtain better hardness and wear resistance coating.The hardness and wear resistance of Al₂CrFeNiMo high entropy alloys coatings are superior to those of traditional Ni-based alloys.（4）Laser cladding Al₂CrFeNiMoSi_xhigh entropy alloys coating.After Si was added,the phase structure remained BCC,the microstructure of the cladding zone was equiaxed,and the bonding zone was planar.With the increase of Si content,the hardness and wear resistance of the coating increase first and then decrease.The average hardness is 2.53～2.98 times of the substrate,the friction coefficient decreases to 48.89%～66.67%of the substrate,and the wear volume decreases 79.45%～95.43%compared with the substrate.Compared with Al₂CrFeNiMo coating,the surface formability and hardness of Si coating are significantly improved.The hardness and wear resistance of the coating were further improved when the Si dosage was 0.25 and 0.5.