Solutions for brazing single-layer diamond tools

Summary and analysis of the research status of brazing single-layer diamond tools:
1. Research on brazing alloys 
1.1 Nickel-based alloys

• Widely used, such as Ni-Cr alloys (containing Cr, Si, B and other elements) through high-frequency induction or vacuum brazing (1050℃-1100℃, heat preservation for several seconds to several minutes), the interface generates carbides such as Cr₃C₂ and Cr₇C₃, which significantly improves the bonding strength.
• Switzerland uses flame spraying combined with argon shielded brazing, and Germany verifies that its grinding efficiency is more than 3.5 times that of electroplating tools. -
• Nanjing University of Aeronautics and Astronautics in China confirmed that the carbide layer is the key to bonding through interface reaction analysis.

 

1.2 Silver-based alloys

• Ag-Cu-Ti brazing filler (such as Ag67%-Cu20%-Ti12%) generates a TiC layer in vacuum brazing, and the bonding strength reaches 133MPa (Harbin Institute of Technology). 
• Ag-Cu alloys with added Cr can be brazed in air, and Cr₃C₂ is generated at the interface to avoid diamond graphitization at high temperatures (Nanjing University of Aeronautics and Astronautics).

 

1.3 Copper-based alloys

• Cu-Sn-Ti-Zr and other alloys form multilayer TiC structures through vacuum brazing (930°C). Xi'an Jiaotong University's homemade copper-based brazing material has a low brazing temperature, reduces thermal damage from abrasive particles, and has a wider adaptability.
• Taiwan University compared vacuum and laser brazing and found that vacuum conditions form continuous TiC films, while laser processes only generate discontinuous layers.

 

2. Brazing process and parameter optimization 
2.1Process method

• High-frequency induction brazing: fast speed (several seconds to tens of seconds), suitable for nickel-based alloys, requires argon or local gas protection.
• Vacuum furnace brazing: precise temperature control (such as 920°C-1000°C, insulation for 10-25 minutes), sufficient interface reaction, and protection of diamond from oxidation.
• Laser brazing: Experiments at Taiwan University show that it is highly efficient (completed in 10 seconds), but the continuity of the interface carbide layer is poor.

 

 

 

2.2 Key parameters

• Temperature: Too high will lead to graphitization of diamond (for example, Ag-Cu-Ti solder has the best bonding strength at 940°C).
• Hot-holding time: Cr-based alloys require a shorter time (6-30 seconds) to prevent excessive diffusion; copper-based alloys require 10 minutes to ensure sufficient interface reaction.
• Protective atmosphere: Argon or vacuum (0.2Pa-6×10⁻³Pa) can reduce oxidation and improve wettability.

 

3. Interface reaction and bonding mechanism

• Transition metals (Ti, Cr) react with the diamond surface to form a carbide layer (Cr₃C₂, TiC, etc.), forming a metallurgical bond.
• The diffusion and enrichment of Cr in nickel-based solder is the key, while silver-based solder relies on the active reaction of Ti.
• The morphology of carbides at the interface affects the bonding strength. For example, shoot-shaped Cr₇C₃ and flake Cr₃C₂ have different effects on bonding stability.

 

4. Abrasive grain optimization arrangement technology
4.1 Purpose:

Increase chip space, reduce grinding temperature, and extend tool life (e.g., optimized arrangement can halve the amount of diamond and double the cutting speed).

 

4.2  Implementation method

• Replication technology: Si template imprints microporous deposited diamond film, suitable for small-size abrasives.
• Shell mold distribution method: Refractory coating pre-set holes to fill brazing material and abrasive grains, suitable for complex curved surface tools.
• Laser rapid prototyping: Use CAD data laser scanning for fixed-point brazing, with high precision but high cost.

 

5. Performance comparison and application effect

•  Compared with electroplating and sintering tools, the abrasive grain exposure height of brazed tools is larger (up to 70%), the bonding strength is improved, and the diamond shedding rate is significantly reduced.

 

5.1 Test cases:

• The life of brazed diamond grinding wheels is more than 3 times that of electroplated grinding wheels, and the high-efficiency grinding temperature is reduced by 30%-50%.
• The efficiency of single-layer brazed saw blades in processing granite is 4.9 times that of electroplated tools.

 

 

6. Current challenges and future directions
6.1 Processing difficulties:

• high-performance control of mass production stability, fine-grained abrasive particles (such as uniform distribution of micro-powder-grade diamond).

 

6.2 Research directions:

• Improvement of brazing material composition (such as adding rare earth elements to regulate wettability).
• Automated production (laser brazing rapid prototyping, research and development of abrasive automatic arrangement equipment).
• Expand application areas (such as oil drill bits, precision ceramic processing, etc.).

 

Research conclusion
Brazing technology significantly improves the performance of single-layer diamond tools through interfacial chemical metallurgical bonding. Nickel-based, silver-based, and copper-based brazing materials each have their own advantages.

 

In the future, it is necessary to overcome the difficulties of large-scale production, combine the optimization of abrasive arrangement with the development of new brazing materials, and promote its widespread application in the field of efficient processing.