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Coated Carbides

(OLD)

There is no definiton before.

(NEW)

The development of coated carbides around 1970 represented a significant advance in cutting-tool technology. Coated carbides are a cemented carbide insert coated with one or more thin layers of wear-resistant material, such as titanium carbide, titanium nitride and/or aluminum oxide. The coating is applied to the substrate by chemical vapor deposition or physical vapor deposition. The coating thickness is only 2.5 to 13 micro meter. It has been found that thicker coatings tend to be brittle, resulting in cracking, chipping, and separation from the substrate.

Coated carbides are used to machine cast irons and steels in turning and milling aperations. They are best applied at high cutting speeds in situations in which dynamicforce and thermal shock are minimal. If these conditions become too severe, as in some interrupted cut operations, chipping of the coating can occur, resulting in premature tool failure. In this situation, uncoated carbides formulated for toughness are preferred. When properly applied, coated carbide tools usually permit increases in allowable cutting speeds compared with uncoated cemented carbides.

(Mikell P. Groover, Fundamentals of Modern Manufacturing: Materials, Processes, and Systems, p.566 )

 

Sheet Metalworking

 

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There is no definition before.

 

(NEW)

 Sheet metalworking includes cutting and forming operations performed on relatively thin sheets of metal. Typical sheet-metal thicknesses are between 0.4 mm and 6 mm. When thickness exceeds abour 6 mm, the stock is usually referred to as plate rather than sheet. The sheet or plate stock used in sheet metalworking is produced by flat Rolling. The most commonly used sheet metal is low carbon steel ( 0.06% - 0.15% C typical).Its low cost and good formability combined with sufficient strength for most product applications, make it ideal as a starting material.

 

(Mikell P. Groover, Manufacturing: Materials, Processes, and Systems, p. 443 )