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<p>Brazing between chemical vapor deposition (CVD) polycrystalline diamond and Kovar alloy was accomplished utilizing an Ag–Cu–In–Ti+B composite filler metal. The effect of boron (B) content (0.4, 0.6, 0.8, and 1.0 wt.%) on the interfacial microstructure and mechanical properties of the joints was systematically investigated, with the brazing process being conducted at 760&#xa0;℃ for 10&#xa0;min. It was found that the typical microstructure of the joint could be characterized as: diamond / TiC / Ag(s.s)+Cu(s.s)+Ag<sub>3</sub>In+Cu<sub>7</sub>In<sub>3</sub>+B+Fe<sub>2</sub>Ti+Ni<sub>3</sub>Ti+(Fe,Ni)Ti+TiB+Cu<sub>4</sub>Ti<sub>3</sub> / (Fe,Co)+Ag(s.s)+Cu(s.s) / Kovar. The addition of B was observed to not only reduce the dissolution and diffusion of the Kovar alloy but also significantly suppress the formation of brittle Ni<sub>3</sub>Ti compounds. Furthermore, Ti-rich and Fe-rich regions were formed within the brazing seam, where reinforcing phases such as TiB and Cu–Ti were in-situ generated. As the B content increased, the width of the dissolution zone in the base metal was gradually reduced, and the diffusion of Ni into the filler metal was effectively inhibited. The shear strength of the joints was observed to first increase and then decrease. The maximum average shear strength of 238.25&#xa0;MPa was achieved at 0.8 wt.% B, which represents a 110% improvement compared to the optimal joint brazed with the original Ag–Cu–In–Ti filler metal. Fracture was identified to primarily occur within the brazing seam, exhibiting a mixed ductile–brittle failure mode.</p>

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Microstructure and mechanical properties of CVD diamond/kovar joints brazed with Ag–Cu–In–Ti+B

  • 期刊论文

  • 发表日期：

    2026年4月11日

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  • Lanbing Sheng,
  • Xiaohang Zhang,
  • Haotian Lu,
  • Yuanxun Shen,
  • Xiaoyu Wang,
  • Zhiqiang Yu,
  • Weimin Long

摘要

Brazing between chemical vapor deposition (CVD) polycrystalline diamond and Kovar alloy was accomplished utilizing an Ag–Cu–In–Ti+B composite filler metal. The effect of boron (B) content (0.4, 0.6, 0.8, and 1.0 wt.%) on the interfacial microstructure and mechanical properties of the joints was systematically investigated, with the brazing process being conducted at 760 ℃ for 10 min. It was found that the typical microstructure of the joint could be characterized as: diamond / TiC / Ag(s.s)+Cu(s.s)+Ag3In+Cu7In3+B+Fe2Ti+Ni3Ti+(Fe,Ni)Ti+TiB+Cu4Ti3 / (Fe,Co)+Ag(s.s)+Cu(s.s) / Kovar. The addition of B was observed to not only reduce the dissolution and diffusion of the Kovar alloy but also significantly suppress the formation of brittle Ni3Ti compounds. Furthermore, Ti-rich and Fe-rich regions were formed within the brazing seam, where reinforcing phases such as TiB and Cu–Ti were in-situ generated. As the B content increased, the width of the dissolution zone in the base metal was gradually reduced, and the diffusion of Ni into the filler metal was effectively inhibited. The shear strength of the joints was observed to first increase and then decrease. The maximum average shear strength of 238.25 MPa was achieved at 0.8 wt.% B, which represents a 110% improvement compared to the optimal joint brazed with the original Ag–Cu–In–Ti filler metal. Fracture was identified to primarily occur within the brazing seam, exhibiting a mixed ductile–brittle failure mode.