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INTERNATIONAL TUNGSTEN INDUSTRY ASSOCIATION

Information on tungsten: sources, properties and uses

Wear Protection

In addition to the use of bulk parts made from cemented carbides, stellites or superalloys, the surfaces of big parts can be protected against wear by different surface modification technologies. 

Plasma transferred arc welding (PTA) and laser cladding are both applied to prepare thick coatings of typically more than 1mm thickness with metallurgical bonding to the substrate.  Predominantly mechanical mixtures of large particles of cast tungsten carbide and binder alloys, eg self-fluxing alloys, are used for coating preparation.

High velocity oxy-fuel (HVOF) spraying is one of the processes in the group of thermal spraying.  It is nowadays the standard process for the preparation of highly wear resistant hardmetal coatings.  The coatings have a predominantly mechanical bonding to the substrate and a typical thickness in the range of 100-500μm.  WC-based compositions with Co or Ni binder (mostly 20-27 vol%) are widely used.  Chromium (up to 20 mass%) alloyed compositions are also widely applied, mostly to improve the corrosion resistance.

Alternatively, cemented carbide parts can be soldered onto selected surface areas.  Chemical vapour deposition starting from tungsten halogenides or alkoxides is a less common method to provide hard, acid-resistant tungsten coatings on bearings, dies, rolls, gauges, etc.

© 2011 International Tungsten Industry Association
Copright image courtesy of L M Berger