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Recommended Reading:

 Manufacturing Engineering and Technology

  Machinery's Handbook

  Marks' Standard Handbook for Mechanical Engineers

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Many tools, usually H.S.S. or Carbide can have their performance significantly improved by coating their surface with a thin layer of material that is very hard and resistant to wear, or possessing a low co-efficient of friction. Commonly used materials are Titanium Nitride (TiN), Titanium Carbide (TiC) and Aluminium Oxide (Al₂O₃).

The use of coatings can impart the necessary wear resistance to a tool without compromising toughness, the cutting forces being accepted by the base metal, or substrate. A good example is a tap threading a tough material such as stainless steel. Taps are subjected to very large torsional shear forces, if a very hard, brittle material such as Carbide were used the tap would shear instantly; H.S.S., although tough, wears quite rapidly cutting Stainless Steel; coating a H.S.S. tap retains toughness but resists wear better even than Carbide. The thickness of these coatings is usually between 2-10 _mm.

2.3.a) TITANIUM NITRIDE (TiN)

Titanium Nitride is commonly used to coat H.S.S. and Carbide drills, taps, reamers and inserts. TiN is very hard; temperature resistant and has a low co-efficient of friction. TiN is a characteristic gold colour and performs well at high cutting speeds and feeds.

2.3b) TITANIUM CARBIDE (TiC)

Titanium Carbide coating a Tungsten Carbide substrate resists flank wear when cutting abrasive materials.

2.4.c) ALUMINIUM OXIDE (Al₂O₃).

Aluminium Oxide, being highly resistant to wear and chemically inert makes a suitable coating for tools; however, this inertness generally makes the bond between substrate and coating quite weak.

Whilst every effort has been made to ensure the accuracy of this site the author can accept no responsibility for any loss, harm or damage howsoever caused by the use of the content of this site.