| WANG Hui-zhao,WANG Yu-ling,JIANG Fu-lin,YANG Fa-zhan,YANG Yong,MA Bao-shan,LIANG Peng.Effects of Laser Remelting on Morphology, Microstructure, Element Distribution and Crack Sensitivity of Al2O3-ZrO2 Laser Cladding Layer on TC4 Titanium Alloy[J],51(12):380-391 |
| Effects of Laser Remelting on Morphology, Microstructure, Element Distribution and Crack Sensitivity of Al2O3-ZrO2 Laser Cladding Layer on TC4 Titanium Alloy |
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| DOI：10.16490/j.cnki.issn.1001-3660.2022.12.039 |
| KeyWord:laser remelting finite element analysis morphology and structure element distribution crack sensitivity |
| Author | Institution |
| WANG Hui-zhao |
School of Mechanical and Automotive Engineering, Qingdao University of Technology, Qingdao , China |
| WANG Yu-ling |
School of Mechanical and Automotive Engineering, Qingdao University of Technology, Qingdao , China |
| JIANG Fu-lin |
School of Mechanical and Automotive Engineering, Qingdao University of Technology, Qingdao , China |
| YANG Fa-zhan |
School of Mechanical and Automotive Engineering, Qingdao University of Technology, Qingdao , China |
| YANG Yong |
School of Mechanical and Automotive Engineering, Qingdao University of Technology, Qingdao , China |
| MA Bao-shan |
School of Mechanical and Automotive Engineering, Qingdao University of Technology, Qingdao , China |
| LIANG Peng |
School of Mechanical and Automotive Engineering, Qingdao University of Technology, Qingdao , China |
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| Abstract: |
| TC4 (Ti-6Al-4V) titanium alloy has the characteristics of high specific strength and good heat resistance. With the same quality, titanium alloy has better mechanical properties than other metals, and is widely used in aviation, aerospace and navigation etc. but its characteristics of poor wear resistance and low hardness limit its wide application. Due to the good hardness, wear resistance and corrosion resistance of ceramic materials, ceramic-metal bonding has become a research hotspot. In recent years, laser cladding, as a new surface modification technology, has provided a new bonding method for metal-ceramic bonding. The work aims to reduce the number of cracks to improve the surface morphology and crack sensitivity of laser cladding coating on TC4 alloy substrate. Laser remelting process was used to treat the cladding layer after laser cladding. The effects of laser remelting on the surface morphology, microstructure evolution and crack sensitivity of Al2O3-ZrO2 cladding layer were studied by combining finite element method with experimental method, and the influence mechanism was also discussed. After laser cladding, the remelting coating was obtained by laser scanning again, and the cladding morphology, microstructure, crack, element distribution and fracture toughness of laser cladding and remelting coating were observed and tested with scanning electron microscope and Vickers hardness tester. Finite element simulation results showed that the temperature of cladding coating rose from 660.23 ℃ to 3 122.3 ℃ from heat affected zone to the top of cladding layer, and the temperature of laser remelting coating rose from 927.61 ℃ to 2 772.9 ℃. By comparing the temperature difference per unit distance, the temperature gradient of remelting coating was smaller than that of cladding coating. In addition, in the Y direction, the residual stress gradually rose from the center to the edge of the coating, while in the Z direction, the residual stress of the remelted coating was obviously relieved, and the residual stress curve was gentle, and the stress gradient was small. Therefore, the laser remelting process can obviously relieve the temperature gradient and residual stress in the bonding zone of the cladding coating. It was found that the surface undulation of laser remelting coating was relieved and the number of surface cracks was reduced. When observing the microstructure of the coating, it was found that the cracks originated from the planar crystal, and several microcracks followed the planar crystal path which consumed the least energy of crack propagation, and finally converged to form the main crack. In this process, the crack energy accumulated continuously, while the plane crystal quantity of the remelting coating was small and the microstructure was dense, which lead to the transgranular propagation of the crack, and the energy consumption of the crack propagation was constant, which effectively hindered the propagation of the crack. The laser remelting process can homogenize the distribution of elements in the top, middle and bottom regions, and increase the fracture toughness of the remelting coating to more than 9 MPa.m1/2, which effectively improved the fracture toughness of the coating and improved the crack sensitivity. By laser remelting, the surface undulation of cladding layer becomes smaller, the number of cracks decreases obviously and the fracture toughness and bond strength are improved obviously. |
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