| LIU Tian,SUN Jie,SONG Jia,YANG Guo-hao,SUN Hai-jing,WANG Bao-jie.Corrosion Behavior of NiCrAl-NiC Seal Coating in Salt Spray Conditions[J],52(1):206-213 |
| Corrosion Behavior of NiCrAl-NiC Seal Coating in Salt Spray Conditions |
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| DOI：10.16490/j.cnki.issn.1001-3660.2023.01.021 |
| KeyWord:NiCrAl-NiC seal coating salt spray test electrochemical test corrosion |
| Author | Institution |
| LIU Tian |
Shenyang Ligong University, Shenyang , China |
| SUN Jie |
Shenyang Ligong University, Shenyang , China |
| SONG Jia |
AECC Shenyang Liming Aero-Engine Co., Ltd., Shenyang , China |
| YANG Guo-hao |
Shenyang Ligong University, Shenyang , China |
| SUN Hai-jing |
Shenyang Ligong University, Shenyang , China |
| WANG Bao-jie |
Shenyang Ligong University, Shenyang , China |
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| Abstract: |
| With the development of aero-engine technology, gas path sealing technology plays an important role in the continuous improvement of aero-engine mechanical efficiency. It is widely used due to the advantages of convenient maintenance, simple manufacturing process and good thermal stability of thermal spraying seal coating. When the seal coating is applied in the environment of high humidity and high salt, its composite metal coating will be seriously damaged. Therefore, the work aims to study the corrosion behavior of NiCrAl-NiC seal coating in high humidity and high salt environment by the salt spray test. The NiCrAl-NiC seal coating was prepared by atmospheric plasma spraying. The surface layer of NiCrAl-NiC seal coating was 1.5 mm thick and the bonding layer of NiAl was about 0.15 mm thick. It was sprayed on the GH907 substrate with a thickness of 2 mm by thermal spraying, and the salt spray test was continuously carried out to the coating. The other five sides of the sample were sealed with silica gel to ensure that only one side of the coating was exposed to salt spray. The test was carried out in accordance with GB/T 1012—2012. The solution was analyzed with 5wt.% pure NaCl solution. The test equipment was DCTC1200P salt spray box. The corrosion time of the samples was 96 h. The samples were continuously sprayed for 24 h, and a set of samples was removed every 24 h. The samples obtained after different time of salt spray test were stored in CS350 electrochemical workstation. The three-electrode cell was used (the reference electrode was saturated calomel electrode, the auxiliary electrode was platinum electrode, and the working electrode was the tested sample) to carry out polarization curve test, electrochemical impedance spectrum test, and scanning electron microscope (TESCAN-MIAR4) observation. Then, the energy dispersive spectrometer spectrum of each selected point collected by the energy spectrometer was used to analyze the elements. X-ray photoelectron spectroscopy test was carried out to the samples after 96 h of salt spray corrosion, and the composition of corrosion products was deeply analyzed. It was observed that the coating surface was loose and had many pores under 500 times electron microscopes, and the corrosion occurred near the surface pores. The results of the energy dispersive spectrometer showed that the content of O element increased in the early stage of corrosion. After continuous salt spray time reached 72 h, Cl and Fe elements were observed, and cracks appeared on the corrosion products on the coating surface. This result showed that the electrolyte solution intruded into the interior of the coating, resulting in corrosion of the substrate. The XPS results after 96 h of corrosion showed that the corrosion products were Al2O3, Ni(OH)2, FeOOH, etc. In the early stage of salt spray test, the corrosion current density obtained by polarization curve decreased, indicating that the corrosion resistance of the coating was enhanced. In the later stage of salt spray corrosion, the corrosion current density increased and the corrosion resistance of the coating decreased. The accumulation of corrosion products in the early stage of the test improves the corrosion resistance of the coating. Due to the gradual increase of corrosion rate with time, corrosion has occurred in the coating in the later stage of the test, and the corrosion products are metal oxides and metal hydroxides. |
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