Brazing Material of Diamond

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Diamond is a kind of polymeric form of carbon element, isomer, the actual composition is carbon, and graphite, carbon black is the same, belongs to non-metal. Diamond brazing can be defined as non-metallic brazing. This kind of brazing is very difficult. In order to solve this problem, some alternative methods have been proposed, for example, diamond and cemented carbide are combined with cemented carbide containing cobalt and other active ingredients by high pressure and high temperature pressing to form a multi-layer composite tool head and then brazing. For example, the diamond powder is mixed with metal powder and reactive metal powder to form a mixed composite tool head. These methods have been widely used. The brazing of this composite material is essentially the brazing between iron matrix and alloy material.

However, in some high-end tool industries, diamond can not be brazed in advance by forming composite materials. It is also necessary to braze by forming an alloy layer between diamond and tool matrix, which is actually an alloy of carbon and metal. There are several problems in the process of diamond welding. Firstly, the solder must have good activity to form a high strength alloy layer with the non-metal carbon. In addition, the welding temperature should not be too high, otherwise the diamond will be destroyed and graphite will be formed. Finally, the working conditions of finished products should be high tolerance, high temperature, high vibration, high shear and other environments, and meet some special requirements, such as conductivity.
The active materials that can activate diamond and form welding layer are boron, titanium, molybdenum, neptunium, beryllium, rubidium and vanadium. In order to meet the requirements of welding strength, corrosion resistance and temperature, these active materials will form filler metals with nickel, silver, copper, tin, aluminum, silicon, gold, chromium and other materials. These materials are very expensive.

In addition, because the application fields are basically tool industries, diamond brazing is often complex in shape, and can not be brazed by simple forming materials (such as brazing rod/wire, brazing ring, brazing disc, etc.). Diamond welding is mostly made of solder paste made of solder alloy powder. It is very difficult to make this kind of solder powder, mainly because the active substance in it is easy to oxidize, invalidate and deteriorate besides boron. It is difficult to control the quality of the finished powder in the production process. The soldering process with powder solder requires high quality of the powder, which is different from the alloy powder used in die casting. In the global market, only a few enterprises can produce qualified and stable brazing alloy powder for diamond welding, and the price is often very high.

Furthermore, vacuum welding is essentially necessary for diamond welding. There are two main reasons, one is to prevent the oxidation of active solder, the other is to protect diamond. This adds to the cost of diamond tools.

Here are some typical and commonly used materials
(a) NiCrBSi (e.g. BNi2) – the cheapest solution
BNi2 (or similar materials) in nickel-based solders can be used to weld diamonds, containing boron as an active material. Its advantage is low price, the price is about 300 yuan per kilogram, in addition, its welding strength and tolerance are also very good. But his disadvantage is also very prominent, welding temperature is high, welding process on Diamond burning is relatively serious.

B) CuSnTi – Variable Material to Meet Requirements
Copper-tin-titanium alloy filler metal can basically meet the majority of cases of diamond brazing. Among them, the copper and tin elements are mainly used to adjust the temperature, and the content of titanium as active element is generally higher than 10%. The advantage of this material is that it can reduce the welding temperature to 900 degrees Celsius or below. The disadvantage is that the price is expensive. Generally, the price is more than 10,000 yuan per kilogram. Some of them reach 30,000 to 40,000 yuan per kilogram. Moreover, the quality guarantee conditions are strict and the shelf life is short. In addition, the working condition tolerance of the welded workpiece is sacrificed due to the reduction of temperature. Finally, the corrosion resistance of this material is insufficient.

C) AgCuTi – a helpless choice for a more demanding environment
In order to remedy the shortcomings of CuSnTi under some conditions, such as strength, corrosion resistance, aging resistance, conductivity and so on, AgCuTi, a more expensive material, has been developed in the industry. As the alloy process between silver and titanium is difficult to control, there is no domestic manufacturer to provide stable quality products. The imported products are expensive, about ten thousand yuan per kilogram. Because of the addition of silver, the performance and price are improved, and the welding temperature is significantly reduced. The lowest brazing temperature is below 850 degrees.
Diamond tools, tool brazing solutions, equipment, process plan, imported silver, copper, titanium, copper, tin and titanium solder paste.

D) Others – high prices
There are many companies in the field of diamond welding. They use less, require more and cost less. This kind of user chooses material more to achieve special performance.
The price of gold, nickel and molybdenum alloys used in nuclear reactors is as high as 100,000 RMB per kilogram, and the price of gold, rhodium, palladium, gold, cobalt and titanium per kilogram is more than six digits.

learn more Diamond Vacuum Brazing Furnace