| JIN Yu-hua,LI Xin-dong,CHAI Li-qiang,ZHANG Xue-xi,QIAO Li,WANG Peng.#$NP Thermal Stability, Mechanical and Tribological Properties of CrN and CrAlN Coatings[J],52(8):182-196 |
| #$NP Thermal Stability, Mechanical and Tribological Properties of CrN and CrAlN Coatings |
| Received:June 27, 2022 Revised:February 10, 2023 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2023.08.013 |
| KeyWord:CrN coating CrAlN coating thermal stability oxidation behavior mechanical property friction and wear property |
| 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 |
| LI Xin-dong |
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 |
| QIAO Li |
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 view of the lack of research on the thermal stability of existing hard CrN and CrAlN coatings for cutting tools and their effects on the tribological properties of coatings, this paper carries out a study on the thermal stability, oxidation behavior, mechanical properties as well as friction and wear properties of CrN and CrAlN coatings. Both types of coatings were prepared by reactive magnetron sputtering. The thermal stability, mechanical properties and tribological properties of the two coatings were characterized by a vacuum thermal desorption system, a field emission scanning electron microscope, an atomic force microscope, an energy dispersive spectrometer, an X-ray diffractometer, a Raman spectrometer, a nano indentation instrument and a ball-on-disk wear tester. In vacuum, for CrN coating, the decomposition and the desorption of N began at about 646 ℃, and the release rates of N peaked at 885 ℃. In the case of CrAlN coating, the releasing of N began at about 722 ℃, and the release rates of N still continued to rise at 1 000 ℃. The Al-N covalent bond with higher bond energy in the lattice of CrAlN could improve the thermal stability of the coating and inhibit the decomposition of N in the coating, increasing the decomposition temperature of N in CrAlN coating. In the atmosphere, CrN coating began to oxidize to form Cr2O3 phase at 600 ℃. The thickness of oxide layer increased continuously with temperature, and the coating was completely oxidized at 900 ℃. CrAlN coating began to oxidize and form crystalline Cr2O3 and Al2O3 phases at 900 ℃. It was apparent that the oxidation resistance of CrN coating was improved due to the doping of Al elements. This was because the amorphous Al2O3 phase formed in the surface layer at the early stage of oxidation could inhibit the oxidation of the coating. On the other hand, the oxide layer formed by the mixture of Cr2O3 and Al2O3 phases had a denser structure than the single Cr2O3 layer, which could mitigate the diffusion of O atoms into the coating. The CrAlN coating had a higher hardness than the CrN coating at the high temperature because the amorphous Al2O3 phase formed at the early oxidation, and the Al-N bond had high bond energy which needed higher temperature to decompose, so that the coating still had high elastic modulus at high temperature. CrN and CrAlN coatings wore slightly at room temperature. With the increase of temperature, the wear mechanism of CrN coating changed from adhesive wear to a mixture of abrasive wear, adhesive wear and oxidation wear, while the CrAlN coating shifted from slight abrasive wear to oxidation wear, and the wear rates of CrAlN coating decreased significantly at 800 ℃. When the temperature increased from 600 ℃ to 800 ℃, both the wear rate and friction coefficient decreased constantly for both types of coatings. The reason was due to the formation of Cr2O3 film with friction reduction and lubrication at high temperature. Compared with CrN coating, the wear resistance of CrAlN coating is obviously improved. This is due to the increased hardness of the CrAlN coating at high temperature. Additionally, the CrAlN coating is oxidized at high temperature to form a dense protective friction film composed of Cr2O3 and Al2O3, which reduces the wear of the coating. Therefore, CrAlN coating is more suitable as a protective coating for materials that wear easily such as tools and molds used at high temperature. |
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