Thermal Spray and Hardfacing
In addition to parts made from cemented carbides, the surfaces of parts can be protected against wear and abrasion by several surface technologies.
High-velocity oxy-fuel (HVOF) spraying is one of the processes in the group of thermal sprays. It is the standard process for the preparation of highly wear-resistant hard metal 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 a Co or Ni binder are widely used. Chromium-alloyed compositions are also widely applied, mostly to improve corrosion resistance.
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, mixtures of fused tungsten carbide, tungsten carbide, or alloys containing tungsten (self-fluxing alloys) are used for coating preparation.
Umicore supplies:
- Coarse tungsten powders (around 25 µm) with an excellent grain size distribution, a low level of impurities, and good flowability
- Fused tungsten carbide powders in different granulometry
- Tungsten carbide powder from 0.7µm to 5µm
- Spherical cobalt powders
- Filamentary nickel powder of 2.5µm