Tools superabrasive

The requirements for an FSW tool in high-temperature materials (HTM) are significant. Obviously, the tool must maintain sufficient strength to constrain the weld material at softening temperatures in excess of 1000 °C (1830 °F). Perhaps less apparent, the tool must also be resistant to fatigue, fracture, mechanical wear, and chemical reactions with both the atmosphere and the weld material. To date, two classes of materials have been found that meet these requirements refractory metal tools and superabrasive tools. 

Superabrasive Tools. The second class of tool materials used for FSW of HTM is superabrasives. Superabrasives are materials that are formed in presses under extreme temperature and pressure. The two superabrasives that have been used in FSW are polycrystalline diamond (PCD) and PCBN. Both materials consist of small crystals of ultrahard material (diamond or CBN) bonded together in a skeletal matrix with a second-phase material that serves as a catalyst for the formation of the matrix. Reference 5 gives a summary of the characteristics of superabrasive materials. 

Superabrasive tools, primarily PCBN, have been used to successfully weld ferritic steels, ferritic stainless steels, austenitic stainless steels, nickel-base superalloys. Invar, and Narloy-Z. Attempts to weld titanium with PCBN tools have been inconclusive. Tool life of 80 m (260 ft) has been demonstrated in FSW of 1018 steel, and very low tool wear has been reported on all other alloys. The primary concern in tool life continues to be fracture, and developments in PCBN grades continue to improve the fracture toughness of the FSW tools. The PCBN tools provide an extremely smooth finish when used for FSW or FSP. 

The main source of boron is a complex compound of boron called borax. About half of the world supply of borax comes from a large deposit in California s Mojave Desert. Borax is used as a cleaning agent and as fireproof insulation. Another compound of boron, boric acid, is used as a disinfectant and as an eye wash. A form of boron nitride is the second hardest known material only diamond is harder. These materials are classified as superabrasives. They are used in grinding wheels, which shape manufactured parts and tools. 

Superabrasive materials can be made only in relatively small pieces, due to the high pressure required for manufacturing. Furthermore, these materials are very difficult or impossible to braze. Therefore, superabrasives are used in a composite tool design, as described by Ref 5. 

The term superabrasives refers to the abrasive grit t) s, cubic boron nitride or diamond, used for abrasive tools. Sometimes the term is also... 

Figure 4 shows an example for the specification of bonded grinding tools with superabrasives. The common abbreviation for diamond grits is (D) and (B) for CBN (Fig. 5). The size of superabrasive grits is often given as mean diameter in micrometer instead of meshlike conventional abrasives. Therefore, the specification of grinding wheels has to be compared...

To fabricate a diamond tool, diamond crystals are blended with a matrix material, normally in the form of a powder, pressed into a shape, and cured or hot-pressed at elevated temperature. Each tool manufacturer has their own techniques, and most of the details are held as trade secrets. The diamond content is specified by the concentration, which in the diamond tool industry refers to 4 times the volume fraction of superabrasive. A tool with concentration 100 therefore comprises 25 vol% diamond. The matrix must be capable of dispersing and supporting the diamond, distrihuting impact and load as the diamond attacks the workpiece, providing controlled wear while allowing crystal protrusion, and holding... 

Diamond and diamond-like carbon CVD, PACVD, ARE Protective coatings Fine particle for IR and UV optics superabrasives, AR coatings, high cutting tool for thermal conductivity aluminium alloys, substrates, micro- wear coatings for electronic devices computer memory discs ... 

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