| MA Shi-zhong,SUN Rong-lu,NIU Wei,ZHANG Lian-wang,JIANG Ting-pu,YANG Jia-wei.Effect of Annealing on Microstructure and Properties of Laser Cladding CoCrFeNiW0.6 High Entropy Alloy Coating[J],52(1):38-46 |
| Effect of Annealing on Microstructure and Properties of Laser Cladding CoCrFeNiW0.6 High Entropy Alloy Coating |
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| DOI：10.16490/j.cnki.issn.1001-3660.2023.01.004 |
| KeyWord:laser cladding high entropy alloy annealing microstructure microhardness friction and wear properties |
| Author | Institution |
| MA Shi-zhong |
School of Mechanical Engineering, Tiangong University, Tianjin , China |
| SUN Rong-lu |
School of Mechanical Engineering, Tiangong University, Tianjin , China;Tianjin Key Laboratory of Advanced Mechatronics Equipment Technology, Tianjin , China |
| NIU Wei |
School of Mechanical Engineering, Tiangong University, Tianjin , China;Tianjin Key Laboratory of Advanced Mechatronics Equipment Technology, Tianjin , China |
| ZHANG Lian-wang |
School of Mechanical Engineering, Tiangong University, Tianjin , China |
| JIANG Ting-pu |
School of Mechanical Engineering, Tiangong University, Tianjin , China |
| YANG Jia-wei |
School of Mechanical Engineering, Tiangong University, Tianjin , China |
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| Abstract: |
| The work aims to further improve the properties of laser cladding CoCrFeNiW0.6 high entropy alloy coating by annealing treatment. RFL-C1000 fiber laser was used to prepare CoCrFeNiW0.6 high entropy alloy coating on the surface of 45# steel. The high entropy alloy coating was annealed at different temperature by SXL-1200 tubular resistance furnace. The processing temperature was 600 ℃, 800 ℃ and 1 000 ℃, and the holding time was 2 h. D8 X-ray diffrotometer (XRD), GeminiSEM 500 thermal field emission scanning electron microscope (FSEM), X-ray energy spectrometer (EDS), HV1000Z microhardness tester, M-2000 friction and wear testing machine, etc. were adopted to analyze and test the microstructure, microhardness and friction and wear properties of the coating. The CoCrFeNiW0.6 high entropy alloy coating was composed of FCC phase and μ phase (Fe7W6), and no new phase was precipitated after annealing at different temperature. After annealing at 600 ℃ for 2 h, the increase of temperature provided energy for atomic diffusion, and the lattice structure defects were alleviated, so that the W atoms further diffused into the solid solution lattice, resulting in lattice distortion, increase of lattice constant and decrease of μ phase volume fraction and μ phase diffraction peak intensity. After annealing at 800 ℃ and 1 000 ℃ for 2 h, W atoms in the solid solution were precipitated as μ-phase compounds, the content of W element in the solid solution decreased, the lattice constant decreased, the volume fraction of μ-phase increased, and the intensity of μ-phase diffraction peak increased. After annealing at 800 ℃ and 1 000 ℃ for 2 h, the microstructure of the coating changed obviously. After annealing at 800 ℃ for 2 h, a large amount of μ phases were precipitated in the microstructure of the coating, and the annealing at 1 000 ℃ for 2 h caused the grain boundary to fracture and decompose, and a large amount of W-rich particles (μ phase) appeared in the grain interior and grain boundary. After annealing at 1 000 ℃ for 2 h, the cladding coating had the highest average microhardness of 475.68HV0.3, which was 45% higher than that of the cladding coating without annealing treatment. The hardness of the heat affected zone tended to be stable and was close to the hardness of the substrate after annealing. In the process of friction and wear, the shedding of μ-phase hard particles aggravated the micro-cutting effect of the grinding wheel on the cladding coating and affected the friction and wear properties of the coating. After annealing at 600 ℃ for 2 h, the average friction coefficient of the coating was the lowest, about 0.226, and the wear mass loss was the least. Compared with the coating without annealing treatment, the wear mass loss was reduced by 28%, and the friction and wear properties of the coating were the best. The increase of annealing temperature did not change the wear mechanism of the coating obviously. After annealing treatment, the furrow shape wear marks on the worn surface became shallower, and a lot of flake small debris appeared, which was dominated by abrasive wear. High temperature annealing can promote the formation of μ phase. After annealing, the hardness of CoCrFeNiW0.6 high entropy alloy coating is significantly improved, and the friction and wear properties of the coating are improved. The strengthening mechanism is solid solution strengthening and second phase strengthening. |
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