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Material Features


  • In order to obtain good results it is necessary that the choice of materials, the heat treatment and the final machining are suitable for coating. Thus  is  necessary a close collaboration between the user and the liner, supported by good metallurgical knowledge.
  • Parts must be electrically conductive.
  • Parts must be able to withstand a temperature of about 500° C without damage (deformation, loss of hardness). (250 ° C  in case of  low temperature coatings). Suitable materials are: tool steels for cold working that have been hardened and tempered at least at 500° C; tool steels for hot working, high-speed steel, carbide, stainless steels and some alloys of copper, aluminium, titanium.
  • Parts must be demagnetized before shipping to avoid the presence of metal residues.
  • It's also possible to coat braised materials if the brazing material is resistant to the vacuum and temperature (parts should not contain cadmium or zinc, the brazing temperature should be above 600 ° C., the braze must not show shrinkage, blowholes or contain residues of flux). Low melting point and extremely volatile elements (zinc, magnesium, tin, lead, etc.) at theirs elementary state or as alloying elements in insoluble form, are harmful because are characterized by strong tendency to "degassing", "liquefy" etc. in the presence of high temperature and vacuum

Surface Features


  • The surfaces of the parts have to be polished and not treated (surface finishes suitable are, for example, grinding, polishing, electro-erosion with thin finishing, lapping).
  • Grinders with worn disc should not be used (due to seizure of the surface). Grinding with blunt mole or inadequate lubrication creates cracks, overheating, changes in microstructure, internal stresses and surface that can cause poor adhesion of the coating.
  • The mirror polish must be made ​​by material removal  and not by "tracing", because in this way residues of the polishing paste would be trapped, causing damages to the coating. The polishing agents must be removed with a suitable solvent, preferably ultrasonically cleaned and oiled immediately.
  • The electro-erosion finishing must be made ​​in order to have a thickness of "white coat" as small as possible (preferably absent).
  • Parts should be oiled (thin layer) to protect them from rust (use hydrophobic oil).
  • For best results the surface roughness Ra of working surfaces must be <0.4 microns  for forming tools and Ra <0.2 microns  for cutting tools.
  • There must be no sharp burrs on the edges.
  • Parts must be free from chips and particulate pollutants (e.g. curing salts) especially in blind holes.
  • Parts must be free of surface treatments such cadmium-treating, galvanizing, tinning, burnishing, phosphatation. Nickel plating, chrome plating and nitriding are usually tolerated  . The parts also must be free of  rust, paint or permanent marking residues.
  • Nitrided  parts (especially extruding screws) must be free of white layer.
  • The best choice is to use new moulds than those who have already worked.
  • Residua of packaging material (eg waxes, glues, PVC, etc.) must be avoided.
  • The photoengraved surfaces can be coated immediately after the process of "photoengraving" without pre-treatments. The surface to be coated must be free of residues of acids or oxidation.
  • Parts should be disassembled (send separate parts); locked mould dies can be treated on request.
  • The cooling caps must be disassembled to optimize the cleaning inside holes of  parts to be coated
  • Internal surfaces can be coated with a width / depth ratio of 1:1.
  • This technology can increase the degree of surface roughness of the particular that in many cases can be restored with a post coating  polishing.

Fixing


  • A way of fixing the part must be provided (hole, thread, stem, etc.).

PACKAGING


  • Inner packing: parts shall be wrapped in paper impregnated with oil or in oil-tight plastic containers. The filler material must avoid any collision between the pieces

DATA TO ADD


  • Designation of kind of tool or its use (only for parts of machines)
  • Kind of material, Werkstoff number.
  • Sizes (scale drawings, sketches), the identification of areas to be treated (in red) and any surface that mustn’t  be treated (in green), the customer must provide protection for steel.
  • Last quenching temperature.
  • Hardness (indicate the measurement points).