| JIN Yu-hua,CHENG Rong,CHAI Li-qiang,ZHANG Xue-xi,WANG Peng.#$NP Thermal Stability of CrN Coatings Prepared by Reactive Magnetron Sputtering[J],51(12):82-90, 108 |
| #$NP Thermal Stability of CrN Coatings Prepared by Reactive Magnetron Sputtering |
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| DOI：10.16490/j.cnki.issn.1001-3660.2022.12.007 |
| KeyWord:CrN coating reactive magnetron sputtering thermal stability oxidation behavior release diffusion barrier |
| Author | Institution |
| JIN Yu-hua |
State Key Laboratory of Advanced Processing and Reuse of Non-ferrous Metals Jointly Established by the Ministry and Province , Lanzhou University of Technology, Lanzhou , China |
| CHENG Rong |
State Key Laboratory of Advanced Processing and Reuse of Non-ferrous Metals Jointly Established by the Ministry and Province , Lanzhou University of Technology, Lanzhou , China;State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou , China |
| CHAI Li-qiang |
State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou , China |
| ZHANG Xue-xi |
State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou , China |
| WANG Peng |
State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou , China |
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| Abstract: |
| In this work, the thermal stability and oxidation behavior of CrN coating were studied in vacuum and atmosphere. The composition and structure changes of CrN coating in different environments at high temperature were investigated. Then, the influence of such composition and structure changes on the performance of the coating was study. These results can provide experimental and theoretical basis for the development of multiple coatings with higher thermal stability in the future, and ultimately improve the performance of CrN coating at high temperature. The CrN coatings were prepared by reactive magnetron sputtering on (100) oriented P-type monocrystalline silicon substrate. The vacuum thermal desorption spectroscopy (TDS), field emission scanning electron microscopy (FESEM), Raman spectroscopy (Raman), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to characterize the thermal stability and oxidation behavior of the CrN coating at different temperatures. The release of N from CrN coating begins at about 664 ℃ and that ends at about 1 000 ℃. Once the temperature is higher than 900 ℃, the release rate of N increases rapidly and that increases to maximum when the temperature rises to 930 ℃. During the heating process, the crystal structure of the coating partially changes from CrN to Cr2N. It should be noted that it completely transforms into CrSi2 phase when the temperature reaches 1 000 ℃. The formation of CrSi2 can be attributed to the release of N, leading to the coating loose. Further, a lot of vacancies generates in the coating, which provide a diffusion channel for the element of Si in the substrate. Thus, the Si in the substrate diffuses to the inside of the coating under the thermal driving effect, and forms a CrSi2 phase by bonding with Cr in the coating. In the atmosphere, the coating begins to oxidize when the temperature increases to 700 ℃, and a dense oxide layer with a thickness of 136 nm is formed on the coating surface. Besides, a transition layer of CrOxN1‒x is formed below the oxide layer, and the peak of Cr2O3 appears in the Raman spectra. When the temperature reaches 800 ℃, the number and intensity of Raman and diffraction peaks of Cr2O3 oxide increase significantly, which means that there are lots of oxide formed on the coating surface and the crystallinity of coating increase. In addition, the oxide particles gradually grow and the oxide layer thickness increases with the increase of temperature. The thickness of oxide layer increases to 429 nm at 850 ℃. When the temperature is higher than 700 ℃, the element diffusion behavior of CrN coating along the thickness direction is the inward diffusion of O element and the outward diffusion of N and Cr element. Note that the released N is enriched below the oxide layer and that not released from the coating. The CrN coating is stable when the temperature is lower than 900 ℃ in vacuum, and that is stable when the temperature is lower than 700 ℃ in atmosphere. The formation of dense Cr2O3 oxide layer in the atmosphere has a diffusion blocking effect for the inward diffusion of O elements and the outward diffusion of N and Cr elements. This blocking effect of the oxide layer protects the interior of the coating and delays the further oxidation of the coating during heating. This is the mean reason for the better thermal stability of CrN coating. The density of Cr2O3 oxide layer formed at high temperature is very important for improving the thermal stability of inner nitride coatings and the oxidation resistance. So, it is possible to further improve the thermal stability and oxidation resistance of binary nitride coatings by adding elements such as chromium, giving rise to a dense oxide layer formed in the binary nitride coatings. |
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