ISSN   1004-0595

CN  62-1224/O4

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热处理NiAl-Bi2O3涂层的宽温域循环摩擦学行为及高低温润滑相再生机制

Tribological Behavior under Wide Temperature Range Cyclic Conditions and Regeneration Mechanism of High and Low Temperature Lubricating Phase of NiAl-Bi2O3 Coating after Heat Treatment

  • 摘要: 采用UMT-3高温摩擦试验机评价了氩气气氛800 ℃热处理等离子喷涂NiAl-Bi2O3涂层在室温至800 ℃的摩擦磨损性能. 通过分析热处理前后涂层及其摩擦表/界面的组成和微结构演变,首次研究了热处理NiAl-Bi2O3涂层的高低温润滑相(NiBi、Bi2O3和NiO)自适应再生机制及宽温域循环摩擦学行为. 结果表明:热处理能使涂层中产生弥散增强的Al2O3和具有中低温润滑性的金属间化合物NiBi,提高了涂层室温至800 ℃的减摩抗磨性能,尤其使涂层在400 ℃的摩擦系数和磨损率分别从0.39和35.56×10−5 mm3/(N·m)降至0.28和8.53×10-5 mm3/(N·m);在800 ℃时,接触表面通过摩擦氧化再次产生润滑相(Bi2O3、NiO),并与增强相Al2O3等自适应形成连续润滑的摩擦层,明显改善了涂层在宽温域、高低温循环下的润滑和抗磨性能. 这种润滑相再生和连续摩擦层形成机制有望进一步提高金属基复合涂层的宽温域服役寿命. 该研究结果对发展固体润滑和抗磨材料新技术具有重要的现实意义.

     

    Abstract: The plasma sprayed NiAl-Bi2O3 composite coating was heat treated under the condition of argon atmosphere of 800 ℃. Then, the friction and wear properties of the resulting heat treated NiAl-Bi2O3 composite coating in the temperature range from room temperature to 800 ℃ were evaluated by UMT-3 high temperature friction tester. By analyzing the evolution of composition and microstructure of NiAl-Bi2O3 composite coating before and after heat treatment, and deeply exploring the frictional surface/interface during the process of friction test at different temperatures, the adaptive regeneration mechanism of high and low temperature lubricating phases (NiBi, Bi2O3 and NiO) within the heat-treated NiAl-Bi2O3 coating was studied for the first time. Meanwhile, the tribological behavior of the heat-treated NiAl-Bi2O3 coating under temperature cycle test conditions of wide temperature range was analyzed in depth. The experimental results showed that the condition of heat treatment of 800 ℃ under argon atmosphere was able to promote the formation of dispersion-enhanced Al2O3 phase and intermetallic compound NiBi phase within the heat-treated NiAl-Bi2O3 composite coating. It was proved that the intermetallic compound NiBi had medium and low temperature lubricity in this study. At the same time, NiAl-Bi2O3 composite coating produced a significant reduction in friction and wear from room temperature to 800 °C through the heat treatment process. Especially when test temperature reached 400 ℃, the friction coefficient and wear rate had a dramatic reduction, where the friction coefficient was reduced from 0.39 before heat treatment to 0.28 after heat treatment, and the wear rate was reduced by a full order of magnitude from 35.56×10−5 mm3/(N·m) before heat treatment to 8.53 × 10−5 mm3/(N·m) after heat treatment. When the test temperature rose to 800 °C, the contact surface of the heat-treated coating generated high-temperature lubricating phase (Bi2O3 and NiO) again through the high-temperature friction oxidation. And then solid lubricants (Bi2O3 and NiO) and reinforced phase Al2O3 adaptively formed a continuous lubricating tribo-layer on the worn surface during the sliding process, and this played a significant synergistic lubrication and anti-wear role. As a result, the lubricating performance and wear resistance capability of the heat-treated NiAl-Bi2O3 coating under the conditions of wide temperature range and high and low temperature cycle condition were significantly improved. It could be concluded that after the heat treatment, there was a mechanism of lubricating phase regeneration and continuous tribo-layer formation on the worn surface of NiAl-Bi2O3 composite coating during the friction process. This mechanism was expected to further improve the service life of metal matrix composite coatings in a wide temperature range. This study had important practical significance for the development of new technologies of solid lubrication and anti-wear materials.

     

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