| XU Hong-yang,LU Jin-bin,PENG Xuan,MA Ming-xing.Microstructure and Properties of Laser Cladding CoCrCu0.4FeNi High Entropy Alloy Coating[J],52(3):418-428, 437 |
| Microstructure and Properties of Laser Cladding CoCrCu0.4FeNi High Entropy Alloy Coating |
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| DOI：10.16490/j.cnki.issn.1001-3660.2023.03.040 |
| KeyWord:laser cladding high-entropy alloys microhardness coating spinodal decomposition CoCrCuFeNi |
| Author | Institution |
| XU Hong-yang |
School of Mechanical Engineering, Suzhou University of Science and Technology, Jiangsu Suzhou , China |
| LU Jin-bin |
School of Mechanical Engineering, Suzhou University of Science and Technology, Jiangsu Suzhou , China |
| PENG Xuan |
School of Mechanical Engineering, Suzhou University of Science and Technology, Jiangsu Suzhou , China |
| MA Ming-xing |
School of Materials and Chemical Engineering, Zhongyuan University of Technology, Zhengzhou , China |
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| Abstract: |
| Due to the low hardness, poor wear resistance and corrosion resistance of the parts made of low carbon steel, the parts fail early in the harsh environment such as high load and corrosive medium environment. Therefore, laser cladding CoCrCu0.4FeNi high entropy alloy coating on Q235 steel substrate with Ni-Cr-B-Si, Co-Cr-B-Si self-fluxing alloy and Cu powder can significantly improve the hardness, wear resistance and corrosion resistance of parts. This article studies the microhardness of CoCrCu0.4FeNi high entropy alloy coating on Q235 steel substrate. Q235 steel with the size of 50 mm×40 mm×8 mm is used as the substrate. The surface of the substrate is polished with sand paper to remove the oxide and cleaned with alcohol to remove the oil and rust. High energy planetary ball mill (F-P2000) is used to ball mill the mixed powder, and the mixed powder after ball milling is coated on the surface of the substrate with a thickness of about 1.5 mm and a width of about 5-6 mm. The laser spot diameter is 4 mm and Ar gas is used as protection gas. Process parameters 1:Ni65, Co157 self-fluxing alloy and Cu powder mass ratio of 1∶1∶1, laser power of 2 500 W, scanning speed of 28 mm/s. Process parameter 2:The powder mass ratio of Ni65, Co157 self-fluxing alloy and Cu is 4.5∶4.5∶1, laser power is 2 200 W and 2 400 W, scanning speed is 9 mm/s and 12 mm/s. Cut the sample by line perpendicular to the scanning direction, grind and polish the coating section, and corrode the sample with aqua regia (concentrated HCl:concentrated HNO3 = 3∶1). Optical microscope (OM, Primotech) is used to observe the macroscopic morphology of the cross section of the coating. Scanning electron microscope (SEM, Quanta FEG 250) and energy dispersive spectrometer (EDS, Oxford) are used to analyze the structure and composition of the cross section of the coating. The phase composition of the coating is analyzed by X-ray diffraction (XRD, D8 Focus). Vickers microhardness tester (JMHVS-1000AT) is used to test the microhardness of the coating and substrate. CoCrCu0.4FeNi high entropy alloy coating with C and B interstitial solid solution is successfully prepared by laser cladding on Q235 steel with Ni-Cr-B-Si, Co-Cr-B-Si self-fluxing alloy and Cu powder. CoCrCuFeNi coating with high Cu content forms a good metallurgical bond with the substrate without macro cracks and pores, but there is serious Cu segregation in the middle and top of the coating. CoCrCu0.4FeNi coating with low Cu content formed a good metallurgical bonding with the substrate, and the composition of the coating is relatively uniform, but there are a few pore defects near the bonding area between the coating and the substrate. The uniform composition of the coating is mainly owing to the good fluidity of the alloy in the melting process due to the addition of B and Si elements. The coating is mainly composed of dendrite and interdendritic structures, and there is a spinodal decomposition region. The main phases of the coating are FCC1 and FCC2. The dendrite phase is FCC1, in which Cu and Ni elements are relatively more, Cr elements are less, and the interdendritic phase is FCC phase, in which Cr elements are more, Cu and Ni elements are relatively less. The lattice constants of the two phases are the same and the compositions are different. There is also a small amount of nano phase, forming CoCrCu0.4FeNi high entropy alloy coating with C and B interstitial solid solution. The thickness of the coating is 2.19-2.58 mm, and the dendrite of the coating is 2.2-7.3 μm. The smaller the dendrite, the higher the hardness. The hardness of CoCrCuFeNi coating with low Cu content is about 280-300HV0.2. The hardness of the substrate is about 110-130HV0.2. It is about 2.5 times that of the substrate, and the smaller the laser power, the higher the scanning speed, the less the dilution of the steel substrate, the finer the dendrite of the coating, the stronger the fine grain strengthening effect and the higher the hardness of the coating. |
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