| MA Bao-shan,JIANG Fu-lin,YANG Fa-zhan,WANG Yu-ling,LIANG Peng.Effect of Laser Energy Density on Microstructure and Properties of Al2O3 Particle Reinforced Ni60A Laser Cladding Coating[J],52(5):364-377 |
| Effect of Laser Energy Density on Microstructure and Properties of Al2O3 Particle Reinforced Ni60A Laser Cladding Coating |
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| DOI：10.16490/j.cnki.issn.1001-3660.2023.05.036 |
| KeyWord:laser energy density Ni60A-Al2O3 coating microstructure element distribution mechanical properties corrosion resistance |
| Author | Institution |
| MA Bao-shan |
School of Mechanical and Automotive Engineering, Qingdao University of Technology, Shandong Qingdao , China |
| JIANG Fu-lin |
School of Mechanical and Automotive Engineering, Qingdao University of Technology, Shandong Qingdao , China |
| YANG Fa-zhan |
School of Mechanical and Automotive Engineering, Qingdao University of Technology, Shandong Qingdao , China |
| WANG Yu-ling |
School of Mechanical and Automotive Engineering, Qingdao University of Technology, Shandong Qingdao , China |
| LIANG Peng |
School of Mechanical and Automotive Engineering, Qingdao University of Technology, Shandong Qingdao , China |
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| Abstract: |
| TiNi alloy is widely used in titanium alloy surface modification because of its excellent toughness, corrosion resistance, biocompatibility, high damping and superelasticity. However, its low hardness often requires the introduction of ceramic reinforced phases to improve mechanical properties. Because of its advantages of heat concentration, fast heating and cooling, small heat affected zone and good controllability, laser cladding technology has greater superiority in the repair of failed parts and the positive modification of strengthened parts. In the laser cladding process, multiple process parameters are coupled together to affect the quality of the cladding coating, and the laser energy density is often selected as the heat input evaluation index. The work aims to study the effect of laser energy density on the microstructure and properties of Al2O3 particles reinforced Ni60A composite coatings, so as to realize the surface strengthening and positive modification of titanium alloy and expand the application range of titanium alloy. The TC4 titanium alloy was cut into 70 mm×15 mm×6 mm cuboid specimens by wire cutting, smoothed with sandpaper and ultrasonically cleaned for 30 min. Ni60A-12%Al2O3 (quality scores) composite powder balls were ground for 2 h and dried at 120 ℃ for 2 h and then pre-coated on clean and smooth TC4 titanium alloy surface. The test was carried out by a FL 020 fiber laser. During the cladding process, the scanning speed was 3 mm/s, the spot diameter was 4 mm, and the laser power was 1 300 W, 1 400 W, 1 500 W, 1 600 W and 1 700 W, respectively. Wire cutting was used to process the cladded workpiece into small specimens of 15 mm×15 mm×6 mm, and the cross section was grounded and corroded with a mixture of HF∶HNO3∶H2O with a volume ratio of 1∶3∶9. The cross-sectional morphology and microstructure of the cladding coating were then observed and analyzed by MERLIN Compact field emission scanning electron microscopy. An energy spectrometer (EDS) was used to analyze the composition and distribution of cladding elements. The cladding phase was analyzed with an X-ray diffractometer. The microhardness of the cladding coating and substrate was measured with the HV-1000 microhardness tester. The friction and wear test was carried out on the UMT friction and wear testing machine, and then the width, depth and wear volume of the wear marks were measured with laser confocal. The wear rate was calculated and the morphology of the surface after wear was observed. Electrochemical corrosion test was carried out at the electrochemical workstation, and the impedance test and polarization test were carried out under this potential after the stable potential was obtained. Ni60A-Al2O3 composite coating with good molding on the surface of TC4 titanium alloy was prepared by laser cladding technology, and the ceramic reinforced phase distribution in the cladding coating prepared with laser energy density of 125 J/mm2 was more uniform, and the impurity phase diffraction peak area was smaller and the element distribution was more uniform. At this time, the mechanical properties of the cladding coating were also the best, and the average microhardness value was 1 132.7 HV0.2, which was about 3.3 times higher than the hardness of the substrate. It had the smallest coefficient of friction and the lowest wear rate, and had good friction reduction and wear resistance. The main reason for the significant improvement in the wear resistance of cladding coating was the formation of the eutectic structure of TiC/TiB2 ceramics. At the same time, the formation of Ni-Ti-Cr and Ti-Ni metal compounds with excellent toughness not only ensured the smoothness of the wear surface, but also effectively relieved the stress concentration of ceramic particles, reducing the occurrence of cracks and friction shedding. The uniform distribution of the ceramic reinforced phase could not only improve the hardness, but also facilitate the formation of a continuous defect-free passivation film and improve the corrosion resistance of the cladding layer. By studying the effect of laser energy density on the microstructure and properties of Ni60A-Al2O3 cladding coating with the control variable method, it is concluded that the cladding coating prepared at 125 J/mm2 has excellent mechanical properties and certain corrosion resistance, which provides help for further expanding the application of titanium alloy. |
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