The bond strength of the bronze bond is high, and this can help to make better use of diamonds. Its wear resistance is good, it can withstand a larger load, and its thermal conductivity is also good. Bronze-bonded diamond tools are mainly used to process non-metallic brittle materials, such as ceramics, glass, stone, concrete as well as gemstone and semi-conductor materials. They are suitable for coarse grinding, half-fine grinding and profile grinding, and are suitable for cutting and edge grinding.

Bronze bonds also have some shortcomings. Its self-sharpening capability is not good. Bronze-bonded diamond tools’ grinding efficiency is lower than the resin-bonded ones’. If they are not properly used, block and heat may be caused, and their dressing is difficult.

The bronze bond has high strength and hardness. Its shrinkage is small and it is easy to generate dispersed shrinking holes. In addition, the thermal conductivity of Cu is only lower than the expensive Ag and is higher than other metals. This helps to decrease the temperature generated in the diamond tools’ working process and avoid burns on the workpiece.

The often adopted metal materials in the bronze bond are the powders of Cu, Sn, Zn and Ag. Sometimes some non-metal materials, such as graphite, are also added. As the objects to be processed and their processing requirements vary, the composition of the bronze bond may also be different. According to the number of metal elements in it, bronze bonds can be categorized into binary-alloy series, ternary-alloy series and multi-alloy series.

1) Binary-Alloy Series: In this series, the Cu-Sn alloy is the most common used. Some graphite is also added into the bonds of this kind.

2) Ternary-Alloy Series: This series is composed by adding a third metal element into the binary-alloy series bonds. The third metal element can be Ag, Ni, Zn, Fe, Pb, etc.

3) Multi-Alloy Series: This series bonds base on the Cu element, and have 3 or more other metal elements, such as Sn, Zn, Pb, Ag, Ni, Co, Fe, Cd, Mo, etc.

1) The pressure in hot press method is low, so the requirement to the press machine is also low, and graphite or cast-iron molds can be used instead of the ones made of high-strength alloy steel.

2) The bonding strength is high, so this method can be applied to produce complex-shape products and the reject rate can be lowered.

3) The products can be sintered with molds, so their expansion and contraction can be controlled and their sizes can be kept well. After stripping, there will be no elastic aftereffect on the pressed blanks.

4) The heating time is short and the production period is also short. This is convenient for small batch production.

5) The low pressure of this method reduces the possibility of diamonds’ crush.

6) The blank materials are sealed in molds, and will not contact with air. The heating time is short. Protective gas may not be used. These simplify the sintering process.

7) The sintering process can be better controlled.

The hot press method also has some disadvantages:

1) There are many production links in this method, and its production efficiency is not high.

2) This method needs many graphite molds, and needs many times of mold loading and stripping.

3) The graphite molds are apt to be damaged, for example, be burned to be defective or be cracked by expansion.

1) The forming of the tools does not need heating equipment, and the operation is easy.

2) The mold need not to be heat-resistant, and has a longer service life.

3) The forming production efficiency is high. The tools can be sintered in bulk.

4) The density of the formed blanks is lower than the one got via the hot press method, and their porosity is higher. This can help the cooling when these tools are used in grinding or cutting.

5) The formed waste products can be recycled timely.

The cold press method also has some disadvantages:

1) After sintering, the size of the pressed blanks changes considerably, especially for those complex-shape tools.

2) The bonding strength between the pressed blank and the tool’s body is low, and issues may arise from these bonding positions.

3) The pressure in the cold press is high. This may lead to the crush of the diamonds, and then influence the performance of the tools. There is a raw blanks’ movement procedure in the cold press method, and the raw blanks may be bumped and broken.

4) The requirement to the forming performance of the raw materials is high. The molds need to be made of high-strength alloy steel.

5) The requirement to the workers’ blank-pressing skills is rather high.

1) Cold-Press Mode: This mode is to first press the working layer (containing diamonds) and the transition layer (not containing diamonds) of the diamond segments to their forms directly on the grinding wheel’s body, and let the segments connect with the wheel’s body via teeth, slots or other manners. Then, put the grinding wheels into sintering furnaces to sinter without press.

2) Semi-Hot-Press Mode: This mode is an improved version of the cold-press mode. When the diamond grinding wheels are being sintered in the furnace, appropriate molds will be applied and some pressure will be added, but the pressure is much lower than the one in the hot-press mode.

3) Hot-Press Mode: This mode is to directly sinter the diamond segments in molds under a certain pressure in the dedicated sintering press machine, and then fix or connect the diamond segments onto the grinding wheel’s body via high-frequency welding, laser welding or mechanical mosaic method.

When deciding what kind of diamond cup wheels should be adopted in your application, you should first examine the hardness and nature of the concrete (or other materials) you are going to grind. If the concrete is hard, the bond of the diamond cup wheel should be softer. Because diamonds are apt to become blunt when grinding hard concrete. The softer bond can be worn down with the blunt diamonds faster, and then make new diamonds beneath be more easily exposed to participate in cutting the hard concrete. If the concrete is relatively softer, the bond should be harder. For diamonds can last longer when grinding softer concrete. The harder bond wears slower, so that it can hold the diamonds longer. This can make better use of the diamonds and prolong the cup wheel’s service life.

There are normally two phases in concrete (and other materials) grinding. The first is coarse grinding and the second is fine grinding (sometimes be called polishing). The two phases need also different diamond cup wheels.

For coarse grinding, the bond should be softer and the diamond toughness should be higher, because in this case the diamonds are more easily to become blunt. The diamond grit should be bigger, normally from 35 grit to 50 grit. For this is coarse grinding and big grit can improve working efficiency. The diamond concentration can be lower.

For fine grinding or polishing, the bond should be harder and the diamond toughness can be lower, for in this case the diamonds can last longer and hard bond can also help the precision of the processing. The diamond grit is normally between 80 grit to 120 grit, depending on practical requirements. The diamond concentration should be higher.

1) Good Adhesion: Resin bond should be able to be distributed on the surface of diamonds evenly, and fix the diamonds firmly on the tool.

2) High Strength: Though resin has good adhesion, it has big fluidity, and is brittle and low-strength. So some kinds of filler materials should be added to improve its strength.

3) Proper Hardness: The hardness of resin bond should fit the speed of diamonds’ wear. If it is too soft, diamonds will fall off the tool without being properly utilized.

4) As High as Possible Heat Resistance: One weakness of resin is low heat-resistance. It is very important to choose some resin that has a relatively better heat-resistance property, and add some filler materials to improve its heat resistance.

5) High Grinding Efficiency and High Processing Finish.

6) The filler materials in the resin bond should be able to dissolve in acid or alkali, so that when the tool is no longer usable, the diamonds in it can be recycled.

Diamond segments have two basic functions. One is holding diamond grains; the other is wearing along with the diamonds’ wearing to let the new sharp diamonds be exposed properly. Besides having a certain hardness and wear resistance, the diamond segment’s bond should also be tough.

Diamond segments for laser welded diamond tools consist of a working layer and a transition layer. The working layer contains diamond grains for cutting or grinding, while the transition layer has no diamonds. It just consists of bond materials, and is used to connect (via welding) the working layer to the body of the diamond tool.

There are various kinds of diamond tools, and because of their superb sharpness, they have been widely applied in many domains, including construction, electronic information, geological mining, medical devices, etc. According to their bond types, manufacture methods and uses, diamond tools can be categorized to the following types:

1) Metal Bonded Diamond Tools: They are made via the steps of mixing diamond grains with metal powder (e.g., Cu, Sn, Fe) evenly, applying powder metallurgy methods to press the mixtures to some shapes and sinter them, and mechanical processing. This type diamond tools are the most often sighted. They include the common diamond saw blades, diamond cup grinding wheels, diamond core drill bits, etc.

2) Resin Bonded Diamond Tools: They are made via the steps of mixing diamond grains with resin powder and some proper fillers (e.g., copper powder), cold pressing or hot pressing them to some shapes, curing, and mechanical processing. This type diamond tools have characteristics of good elasticity, good impact tolerance, good self-sharpening capability, and high grinding efficiency. An example of this type diamond tools is diamond polishing pads.

3) Plated Diamond Tools: They can be made by using electroplating methods to plate the tool’s surface with one or several metal layers, in which diamond grains are distributed evenly. Another method is using CVD (Chemical Vapor Deposition) method to deposit a layer of dense polycrystalline diamonds on the tool’s surface. Plated diamond tools include some diamond cutting tools, drilling tools, etc. They have characteristics of high efficiency, long life and high grinding precision.

4) Ceramic Bonded Diamond Tools: They are made via the steps of mixing diamond grains with glass and ceramic powder, pressing the mixtures to shapes, sintering, dressing, and sharpening. This type diamond tools include some diamond grinding tools. Their characteristics are: good chemical stability, small elastic deformation, high brittleness, etc.

5) Polycrystalline Diamond (PCD): They are normally made by sintering many micro-size single diamond crystals in high temperature and high pressure. The crystals in PCD are arranged disorderly, so the hardness and wear resistance of PCD in all directions are almost the same. PCD also has good fracture toughness and good thermal stability. It can be applied in geological drill bits, machining tools, etc.

6) Polycrystalline Diamond Composite or Compacts (PDC): They are made by combining some layers of polycrystalline diamonds (PCD) with a layer of cemented carbide liner in high temperature and high pressure. PDC has the advantages of diamond’s high wear resistance and carbide’s good toughness.

7) High-Temperature Brazed Diamond Tools: They are made by brazing a single layer of diamonds onto the tool via some solder under the temperature of over 900°C. This tool is a newly developed product. Its making technologies include vacuum brazing and atmosphere-protected brazing. This tool has great advantages, because the solder can hold the diamonds very firmly, the single layer of diamonds’ exposed height can be 70% – 80% of their sizes, and the diamonds can be regularly arranged on the tool. This tool has been applied in many industries, and its future should be good.