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<p>To enhance corrosion resistance and reduce costs of oil pipeline precision components, this study utilizes vacuum diffusion bonding to join conventional TC4 titanium alloy (TC4) with CoCrFeNi high-entropy alloy (HEA), ensuring required welding precision for industrial applications. An investigation was carried out to explore how the bonding temperature influences the microstructure evolution and mechanical properties of the resulting joint. The typical interfacial microstructure of the joint comprises TC4 base metal, a TC4 diffusion layer, an XTi<sub>2</sub> layer, a YTi layer, a Z<sub>2</sub>Ti layer, a CoCrFeNiTi<sub>0.5</sub> high-entropy layer, and CoCrFeNi base metal. The XTi<sub>2</sub> layer exhibited a discontinuous, needle-like morphology, while the other layers displayed smooth interfaces with clearly defined interlayer boundaries. At 800&#xa0;°C, the mechanical performance of the CoCrFeNi/TC4 diffusion-bonded joint was the highest with an average shear strength of 164&#xa0;MPa, equivalent to 70% of the CoCrFeNi base metal’s strength. At temperatures below 800&#xa0;°C, the poor performance of the joint can be attributed to incomplete bonding and void defects at the interface. However, when the bonding temperature exceeds 800&#xa0;°C, accelerated atomic diffusion promotes the formation of abundant IMCs. Concurrently, the mismatch in coefficients of CTE between the materials induces escalating internal stress. This synergistic effect of IMC formation and thermal stress leads to microcrack initiation at the interface when the bonding temperature reaches 850 and 900&#xa0;°C. These synergistic effects reduce the mechanical properties of the joints.</p>

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Effect of Temperature on Microstructure and Mechanical Properties of CoCrFeNi/TC4 Diffusion-Bonded Joints

  • 期刊论文

  • 发表日期：

    2025年10月29日

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  • Kai Yang,
  • Qingdong Qin,
  • Juan Li,
  • Honglong Zhao,
  • Nianbing Zhang

摘要

To enhance corrosion resistance and reduce costs of oil pipeline precision components, this study utilizes vacuum diffusion bonding to join conventional TC4 titanium alloy (TC4) with CoCrFeNi high-entropy alloy (HEA), ensuring required welding precision for industrial applications. An investigation was carried out to explore how the bonding temperature influences the microstructure evolution and mechanical properties of the resulting joint. The typical interfacial microstructure of the joint comprises TC4 base metal, a TC4 diffusion layer, an XTi2 layer, a YTi layer, a Z2Ti layer, a CoCrFeNiTi0.5 high-entropy layer, and CoCrFeNi base metal. The XTi2 layer exhibited a discontinuous, needle-like morphology, while the other layers displayed smooth interfaces with clearly defined interlayer boundaries. At 800 °C, the mechanical performance of the CoCrFeNi/TC4 diffusion-bonded joint was the highest with an average shear strength of 164 MPa, equivalent to 70% of the CoCrFeNi base metal’s strength. At temperatures below 800 °C, the poor performance of the joint can be attributed to incomplete bonding and void defects at the interface. However, when the bonding temperature exceeds 800 °C, accelerated atomic diffusion promotes the formation of abundant IMCs. Concurrently, the mismatch in coefficients of CTE between the materials induces escalating internal stress. This synergistic effect of IMC formation and thermal stress leads to microcrack initiation at the interface when the bonding temperature reaches 850 and 900 °C. These synergistic effects reduce the mechanical properties of the joints.