| ZHANG Shuai,LIU Shu-feng,LU Fei,LI Hui,LIU Xiao-yu.Preparation Technology and Properties of Al Protective Coatings on the Surface of Sintered NdFeB Magnet Via Plasma Spray[J],51(12):208-216 |
| Preparation Technology and Properties of Al Protective Coatings on the Surface of Sintered NdFeB Magnet Via Plasma Spray |
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| DOI：10.16490/j.cnki.issn.1001-3660.2022.12.021 |
| KeyWord:sintered NdFeB plasma spray Al protective coating anticorrosion properties magnetic properties |
| Author | Institution |
| ZHANG Shuai |
State Key Laboratory of Baiyunobo Rare Earth Resource Researches and Comprehensive Utilization, Baotou Research Institute of Rare Earths, Inner Mongolia Baotou , China |
| LIU Shu-feng |
State Key Laboratory of Baiyunobo Rare Earth Resource Researches and Comprehensive Utilization, Baotou Research Institute of Rare Earths, Inner Mongolia Baotou , China |
| LU Fei |
State Key Laboratory of Baiyunobo Rare Earth Resource Researches and Comprehensive Utilization, Baotou Research Institute of Rare Earths, Inner Mongolia Baotou , China |
| LI Hui |
State Key Laboratory of Baiyunobo Rare Earth Resource Researches and Comprehensive Utilization, Baotou Research Institute of Rare Earths, Inner Mongolia Baotou , China |
| LIU Xiao-yu |
State Key Laboratory of Baiyunobo Rare Earth Resource Researches and Comprehensive Utilization, Baotou Research Institute of Rare Earths, Inner Mongolia Baotou , China |
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| Abstract: |
| The air plasma spraying process is a novel surface protective technology on sintered NdFeB, which have a quantity of advantage on preparation process, corrosion resistance and other properties. There are some researches had been reported about cold spraying and part of hot spraying technology applied on surface protective. Although the air plasma spraying have been mentioned seldom, it can greatly improve the corrosion resistance of NdFeB magnets and can provide new ideas for industrial applications in NdFeB protection. The work aims to prepare Al protective coatings on the surface of sintered NdFeB magnets by atmospheric plasma spraying technology, so as to strengthen the protection of NdFeB magnets by plasma spraying technology. In this work, sintered NdFeB magnets with dimensions of 30 mm×20 mm×4 mm were degreased, dried in air, and then grit-blasted prior to deposition. All specimens were in the state of demagnetization. Pure aluminum powders (>99.9%) were divided into 20-40 μm, and then were applied to spray onto the NdFeB substrate. As a result, with the spraying current increased from 400 A to 600 A, through observing the surface and cross-section morphology with SEM (SIGMA500), the best spraying current was 500 A, under which the surface of coating was dense without obvious sputtering stacking and unmelted particles. Finally the sprayed current was 500 A, the carrier gas flow rate was 1 800 L/h, the powder feed rate was 0.1 r/min, the distance was 150 mm. Under this process parameter, with the spraying number increased from 20 to 50 times, the thickness of coating had increased; when the spraying number reached to 30 times, the average thickness was up to 40 μm and the adhesive strength was over 15.5 MPa. Then, the corrosion resistance of coatings with different thickness were tested through electrochemical workstation (Ivivum) and salt spray test (YWX-750), and magnetic properties were tested with impulse magnetic field magnetometer (Metis Instruments). The Al coating was a sacrificial anode to protect the substrate and the self-corrosion voltage was about –1.1 V vs saturated calomel electrode, which had no apparently influence in thickness of Al coating. The self-corrosion current was smaller two orders of magnitude after deposition of Al coating on the NdFeB matrix, which decreased from 1.18´10–4 A/cm2 to 5.12´10–6–6.77´10–6 A/cm2; as the thickness of Al coatings increased, the corrosion resistance of Al coatings was increased, and that of coatings as thick as 70 μm was over 300 h. With the thickness of coating increased from 0 to 70 μm, the coercivity of the magnet was slightly increased and the residual magnetism was decreased from 2.0% to 4.26% of the original sample. Plasma spraying coating with excellent performance in adhesion, corrosion resistance and preparation process were used to prepare Al protective coatings and achieve the great protection to NdFeB magnet. The sprayed Al coating is a sacrificial anode to protect the substrate and have almost no damage to magnet properties. |
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