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

◎ 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.

◎ 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 alloy with Cr added can be brazed in air, and Cr₃C₂ is generated at the interface to avoid graphitization of diamond at high temperature (Nanjing University of Aeronautics and Astronautics).

◎ Copper-based alloys

◎ Cu-Sn-Ti-Zr and other alloys are brazed in vacuum (930℃) to form a multilayer TiC structure. 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 a continuous TiC film, while the laser process only generates a discontinuous layer.

2. Brazing process and parameter optimization

◎ Process 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℃-1000℃, 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.

◎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).

◇Housing 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 solders is the key, while silver-based solders rely 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

◎ 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).

◎ 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.

◎ 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

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

◎ 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 conclusions

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

In the future, we need 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 high-efficiency processing.