Can diffusion welding vacuum furnace brazing diamond?

08-18-2025       Author: KJ technology

The diffusion welding vacuum furnace can brazing diamond and has significant advantages in diamond tool manufacturing. The specific analysis is as follows:

1. Technical feasibility: compatibility between vacuum environment and diamond brazing

Prevent oxidation and graphitization

Diamond is prone to react with oxygen at high temperatures to produce carbon dioxide (ignition point 850~1000 ℃), or convert to graphite (above 1500 ℃) in high-temperature oxygen free environments. The vacuum furnace can effectively isolate oxygen and prevent diamond oxidation or graphitization by maintaining an extremely low vacuum degree (such as 6.7 × 10 ⁻ ³ Pa), ensuring the stability of the physical properties of diamond during brazing.

Promote wetting and diffusion of brazing materials

Vacuum environment can reduce volatile impurities (such as hydrogen) in brazing materials, lower porosity, and improve the wettability of brazing materials on diamond and substrate. For example, when using Ni Cr based brazing materials, vacuum conditions can promote the enrichment of Cr elements on the surface of diamond, forming carbide layers (such as Cr ∝ C ₂, Cr ₇ C ∝), achieving metallurgical bonding, and significantly improving bonding strength.

2. Process advantage: synergistic effect of diffusion welding and brazing

High strength bonding

Diffusion welding uses high temperature pressure to diffuse atoms at the contact surface, forming metallurgical connections. By combining brazing technology, a dual bond can be formed between diamond and substrate (such as steel, hard alloy):

Brazing layer: The gap is filled by melting the brazing material to achieve preliminary connection.

Diffusion layer: pressurized and insulated in a vacuum furnace to promote atomic diffusion, eliminate interface defects, and form a stronger metallurgical bond.

This process can achieve a diamond exposure height of over 70% of the particle size and increase tool life by more than three times.

Adaptability to complex structures

The vacuum diffusion welding furnace can process irregular diamond tools such as saw blades and drill bits, and achieve mass production through multi chamber design or continuous tunnel furnaces. For example, the mesh belt continuous tunnel furnace can complete brazing under the protection of ammonia decomposition atmosphere, with high production efficiency and uniform heating of the workpiece.

Material Compatibility

Vacuum furnaces are suitable for various brazing material systems, including:

Silver based brazing material: Highly versatile, suitable for most diamond tools, with a melting point of 600~750 ℃, good plasticity, and impact resistance.

Nickel based brazing material: mainly used for vacuum brazing of single-layer diamond tools, such as Ni Cr alloy, which can form a carbide layer to enhance bonding.

Copper based brazing materials: tools suitable for working at high temperatures, such as argon arc brazing, laser brazing, or immersion brazing of petroleum drill bits.

3. Typical application cases

Single layer diamond tool

AKChattopadhyay et al. from Switzerland used flame spraying to deposit Ni-Cr-Si-B brazing material onto a steel substrate. After arranging diamonds, induction brazing was carried out under argon protection (1080 ℃, 30 seconds) to achieve a strong bond between the diamond and the substrate. The Fourth Military Medical University and Xi'an Jiaotong University in China use NiCr13P9 alloy brazing material, which is brazed under a pressure of 4.9MPa at 950 ℃ in a vacuum furnace (0.2Pa). The diamond cutting edge height is high, and the tool life is significantly improved.

Exploration of multi-layer diamond tools

Although current vacuum brazing is mostly limited to single-layer tools, the "impregnated" effect of multi-layer diamond has been initially achieved by optimizing the composition of the brazing material (such as adding active elements Ti and Cr) and process parameters (such as segmented heating and gradient pressure). For example, Taiwan's China Grinding Wheel Company has launched a single-layer uniformly distributed diamond high-temperature brazed bead, which reduces diamond usage by 50% while increasing cutting speed by 2 times.