Unveiling the TiZrNbTaFeCx high entropy alloy carbide coatings fabricated by superimposed HiPIMS-MF technique — effect of carbon contents on the microstructure, mechanical properties, and corrosion resistance
高碳含量高熵合金碳化物鍍層之微結構、機械性質與腐蝕行為研究
📄 英文摘要
In this research, TiZrNbTaFe high entropy alloy (HEA) and five TiZrNbTaFeCx HEA carbide coatings with different carbon contents were fabricated by a superimposed HiPIMS-MF system under different C₂H₂ gas flow rates. The phase structure of the coating changed from amorphous to FCC at 32.40 at.% carbon. Hardness increased from 7.7 to 22.1 GPa as the carbon content increased from 0 to 32.40 at.%, then decreased to 19.5 GPa at 35.78 at.% C due to too much soft amorphous carbon phase. The HEA coating with the highest carbon content of 35.78 at.% exhibited the best wear resistance, with a lower coefficient of friction of 0.21 and the lowest wear rate of 3.80 × 10⁻⁶ mm³N⁻¹m⁻¹. According to the potentiodynamic polarization and electrochemical impedance spectroscopy tests, the TiZrNbTaFe coating exhibited excellent corrosion resistance in 0.5 M H₂SO₄, which is 802.7 times better than that of bare AISI 52100. We can conclude that the 35.78 at.% C contained TiZrNbTaFeC HEA carbide coating exhibited a hardness of 19.5 GPa, excellent tribological performance, and the second-best corrosion resistance, which can be used in severely corrosive and stress bearing environments.
📄 中文摘要
本研究利用重疊式 HiPIMS-MF 濺鍍系統，在不同 C₂H₂ 氣體流量條件下，製備 TiZrNbTaFe 高熵合金（HEA）及其五種不同碳含量的 TiZrNbTaFeCx HEA 碳化物鍍層。當碳含量達 32.40 at.% 時，鍍層相結構由非晶相轉變為 FCC 相。硬度隨碳含量由 0 增加至 32.40 at.% 而從 7.7 GPa 提升至 22.1 GPa，隨後因過量軟性非晶碳相形成而於 35.78 at.% C 時下降至 19.5 GPa。含 35.78 at.% 碳之 HEA 鍍層展現最佳耐磨特性，摩擦係數低至 0.21，磨損率為 3.80 × 10⁻⁶ mm³N⁻¹m⁻¹。根據動電位極化與電化學阻抗能譜測試，TiZrNbTaFe 鍍層於 0.5 M H₂SO₄ 中展現優異腐蝕抗力，較裸材 AISI 52100 優異達 802.7 倍。本研究結論指出，含 35.78 at.% 碳之 TiZrNbTaFeC HEA 碳化物鍍層硬度達 19.5 GPa，具備優異的 tribological 性能與次佳腐蝕抗力，適合應用於高腐蝕性與高應力環境。
🔬 五項核心重要發現
鍍層結構隨碳含量由非晶相轉變為 FCC 結構，當碳含量達 32.40 at.% 時觀察到明顯的 (111)、(200)、(220) 繞射環，確認 FCC 奈米晶相之形成。
硬度隨碳含量增加而上升，於 32.40 at.% C 時達峰值 22.1 GPa；進一步提高碳含量至 35.78 at.% 時，過量軟性非晶碳相導致硬度下降至 19.5 GPa，呈現鐘形曲線關係。
含 35.78 at.% 碳之鍍層展現最低摩擦係數（0.21）與最低磨損率，歸因於緻密 FCC 結構與碳化物強化效應。
TiZrNbTaFe 鍍層於 0.5 M H₂SO₄ 腐蝕環境中，腐蝕電流密度極低，腐蝕抗力較裸材 AISI 52100 優異達 802.7 倍，證實高熵合金碳化物鍍層之優異耐蝕潛力。
X 光光電子能譜分析顯示 TiC、ZrC、NbC、TaC、FeC 等金屬碳化物特徵峰，證實碳原子成功摻入並與各金屬形成鍵結。
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