| HU Qiyun,WANG Chenyang,JIANG Huazhen,ZHAN Jian,LI Zhengyang.Design and Microstructure Properties Analysis of Laser Cladding Coating on Nitrided H13 Steel[J],54(5):203-216 |
| Design and Microstructure Properties Analysis of Laser Cladding Coating on Nitrided H13 Steel |
| Received:February 27, 2024 Revised:April 28, 2024 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2025.05.016 |
| KeyWord:laser repair nitrided H13 steel nitrogen precipitation coating design micro-hardness electrochemical corrosion |
| Author | Institution |
| HU Qiyun |
Wide Field Flight Engineering Science and Application Center, Institute of Mechanics, Chinese Academy of Sciences, Beijing , China;College of Engineering Science, University of Chinese Academy of Sciences, Beijing , China |
| WANG Chenyang |
College of Mechanical Engineering, Hebei University of Science & Technology, Shijiazhuang , China |
| JIANG Huazhen |
Wide Field Flight Engineering Science and Application Center, Institute of Mechanics, Chinese Academy of Sciences, Beijing , China |
| ZHAN Jian |
Wide Field Flight Engineering Science and Application Center, Institute of Mechanics, Chinese Academy of Sciences, Beijing , China |
| LI Zhengyang |
Wide Field Flight Engineering Science and Application Center, Institute of Mechanics, Chinese Academy of Sciences, Beijing , China |
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| Abstract: |
| In the industry, the surface of H13 tool steel is generally nitrided to improve its properties, thus reducing the frequency of maintenance and replacement. As an advanced surface modification technology, laser cladding is widely used in surface strengthening and repairing. However, nitrogen will precipitate and may form nitrogen pores during laser repair of nitrided H13 tool steel. In order to solve this problem, two types of cladding materials containing Ti and Co were designed based on the thermodynamic principle of melt pool reaction. The distribution and release mechanism of nitrogen element were studied. And laser cladding coatings with good properties but no obvious pores and cracks were prepared on nitrided H13 tool steel. Laser cladding experiments were conducted with mixed powder of H13 and Stellite, as well as mixed powder of H13 and Ti as cladding materials. The process was optimized by changing laser line energy density, and the composition was optimized by changing the mass ratio of mixed powder. Then, two schemes were tested. In the first design, laser remelting pre-treatment was carried out on the nitrided surface of the substrate, followed by laser cladding the mixed powder of H13 and Stellite alloy. In the second design, with the mixed powder of H13 and Ti with different ratios as the base material, then the mixed powder of H13 and Stellite alloy was cladded on the base material. The microstructure of samples was characterized by optical microscope, scanning electron microscopy, electron backscatter diffraction and X-ray diffraction. Performance testing included micro-hardness tests and electrochemical corrosion experiments. The average hardness of the nitrided H13 steel was about 530HV. And its corrosion current density was 1.68×10–5 A/cm2. Generally, during laser cladding on the surface of nitrided H13 steel, nitrogen elements were enriched in the bonding zone, resulting in component segregation and poor corrosion resistance. The results of the first design showed that laser remelting pre-treatment could induce the release of nitrogen. After laser cladding, the microstructure was mainly martensite and retained austenite. The average hardness of the laser cladding coating was about 550HV. Compared with the nitrided H13 steel substrate, its corrosion resistance was greatly improved, and the corrosion current density was 7.57×10–7 A/cm2. The results of the second design showed that with the increase of Ti content from 0% to 10% in the mixed powder of H13 and Ti, there was a significant difference in the metallurgical transition zone between the coating and the substrate. Among them, H13+10%Ti coating had the best quality with good metallurgical bonding between the coating and the substrate. Its microstructure was martensite and dispersed carbides. And the microstructure of H13+50% Stellite coating on it was homogeneous and dense, mainly composed of martensite, including a small amount of retained austenite. Its average hardness was about 575HV. And the corrosion current density of the coating surface was 2.48×10–6 A/cm2, which was much lower than that of the nitrided H13 steel substrate, which meant that the corrosion resistance was significantly improved. In this article, the precipitation and release mechanism of N element is analyzed by microstructure observation and performance testing. Through designing coating compositions and optimizing processing parameters, laser cladding coatings with high hardness and good corrosion resistance are prepared by laser melting deposition technology, which solve the problem of nitrogen pore formation and component segregation in bonding zone between the coating and the substrate during strengthening and repairing of H13 nitrided tool steel. |
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