| LANG Tao,LIU Gang,HE Weihuan,LI Yong,LIU Jiajiang.Effect of High Roughness NiCrB Bond Coat on Properties of Ceramic Particle Reinforced Polymer Composite Coating[J],53(5):205-213 |
| Effect of High Roughness NiCrB Bond Coat on Properties of Ceramic Particle Reinforced Polymer Composite Coating |
| Received:May 25, 2023 Revised:October 31, 2023 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2024.05.021 |
| KeyWord:nickel-based bond coat arc spraying high roughness high adhesion corrosion resistance |
| Author | Institution |
| LANG Tao |
Sichuan Huaneng Kangding Hydropower Co., Ltd., Chengdu , China |
| LIU Gang |
Xi'an Thermal Power Research Institute Co., Ltd., Xi'an , China |
| HE Weihuan |
Sichuan Huaneng Kangding Hydropower Co., Ltd., Chengdu , China |
| LI Yong |
Xi'an Thermal Power Research Institute Co., Ltd., Xi'an , China |
| LIU Jiajiang |
Sichuan Huaneng Kangding Hydropower Co., Ltd., Chengdu , China |
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| Abstract: |
| The hydraulic flow components, such as turbines and volutes, in high-sediment rivers are susceptible to surface wear, cavitation erosion, and corrosion due to the presence of high-sediment water flows. These issues can lead to rapid failure of these components, thereby affecting the safety and stable operation of the power plant. Polymer-based composite coatings offer several advantages over other methods, including low cost, excellent cavitation resistance, and high construction flexibility, which have been widely employed for surface protection of carbon steel parts. However, polymer-based composite anti-cavitation coatings often exhibit poor bonding with the carbon steel substrate, and localized coating damage can lead to rapid oxidation and rusting of the carbon steel, resulting in peeling of the coating. To address these problems, in the present paper, it is proposed to greatly enhance the bonding strength and increase the corrosion resistance of the polymer-based composite coating by introducing a NiCrB bond coat with high surface roughness. The NiCrB bond coat was prepared on the carbon steel surface by using arc spraying technology, which offered high flexibility and low cost. During this process, the nickel-based wire was melted and partially evaporated due to the high arc temperature of up to 6 000 ℃. The liquid-gas two-phase deposition ensured a high surface roughness, thereby strengthening the mechanical locking between the polymer-based composite coating and the low carbon steel substrate. Consequently, the bonding strength and service life of the coating could be improved. Subsequently, a ceramic-reinforced polymer coating was coated onto the NiCrB bond coat. The surface morphology and roughness of the bond coat were measured with a laser confocal microscope. The bonding strength of the coating was tested with an Instron 1195 tester according to the ASTM C633 standard. The corrosion resistance of the coating was evaluated through measurements of open circuit potential, impedance spectrum, polarization curve, and neutral saltfog spray corrosion. The results indicated that, through parameter control, regularly arranged convex particles could be formed on the surface of the NiCrB coating after droplet gasification. The surface roughness of the coating was significantly higher than that of conventional thermal spraying coatings, ranging from Ra 10.95-37.24 μm, while the porosity remained below 1.5%. The addition of a high-roughness dense NiCrB layer increased the bonding strength of the polyurethane-based composite coating from 13.6 MPa to 30.5 MPa. Moreover, the incorporation of NiCrB in the substrate elevated the open circuit potential from −0.73 V to −0.54 V, the corrosion potential from −0.76 V vs. SCE to −0.58 V vs. SCE, and the charge transfer resistance from 1 729 Ω.cm2 to 8 425 Ω.cm2. It was found that even the top polymer-based coating was cracked, the sample with a NiCrB bond coat exhibited no visible rust spots after a 300 h neutral salt fog spray test, representing an 11-fold increase compared with the sample without the bond coat. In summary, arc-sprayed NiCrB coating allows for effective control of surface roughness within a wide range. The enhanced roughness significantly improves the bonding strength of the polymer-based composite coating. The superior corrosion resistance of the coating ensures long-term protection and the extended service life of hydraulic flow components. |
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