TD / TRD Coatings

Thermoreactive Diffusion Coating Process - Molten BathThermoreactive Diffusion (TD or TRD) coating processes are available as part of our standard line of wear-resistant coatings.  TD coatings are most commonly used in metal-forming applications, and work well to fill application gaps where CVD coatings may not be optimal.   The full range of processes provided by Richter Precision Inc. allows us to supply the best coating solution in order to unlock the full potential of your tools.

What is TD Coating?

Thermoreactive Diffusion (TD or TRD) is a high temperature coating process for producing metal carbides (typically vanadium carbide) on the surface of a carbon-containing substrate. This is a multi-stage coating process which utilizes a pre-heat cycle, a coating segment, ultra-sonic cleaning, heat-treating, and post-coating polishing. The coating segment is performed in a molten bath [typically consisting of a solute (Borax), a metal source, and a reducing agent]: carbide-forming compounds in the bath react with carbon in the substrate and produce metal carbides on the substrate surface. TD coatings exhibit a diffusion type bond, thereby providing superb adhesion between the metal carbide layer and the substrate. This bonding characteristic, combined with the coating’s high micro-hardness, provides excellent resistance to the types of wear and galling often seen in many metal-forming processes.

General Characteristics of TD Coatings

  • Processed in an elemental salt bath
  • Reactions take place on the surface of the parts, with the coating exhibiting a diffusion style bond to the substrate
  • Metal carbide films exhibit a high micro-hardness (3400-3800 HV), typically in excess of 80 HRc, depending on film composition
  • Coatings will typically exhibit a low coefficient of friction (0.15 – 0.3) depending on film composition
  • TD is an additive process, with an average film thickness of .006 – .009 mm., or .00024 – .00035 inches
  • TD Coated Forging DieHigh processing temperature (~ 1875° F)
  • TD is better able to coat internal surfaces than a PVD process.
  • Pre- and post-coating polishing can achieve good final finishes
  • Post-coating heat treating is required on steel tools

Special TD Processing Notes

  • Air hardened tool steels and High Speed Steels are recommended for the TD process
  • Steels must have ≥.3% carbon content in order to form a coating layer
  • Oil-hardened tool steels are not recommended for this process
  • When coating carbide (WC) tools, we recommend carbide grades with ≥10% Co binder (carbides with Ni, Ti or other binders are not suitable for this process)

TDkote™ TD Coatings

Proprietary NameCompositionColorThickness (microns)Micro-Hardness (HV)Coefficient of FrictionMaximum Working TemperatureCoating Process Temperature
TDkote™+SVC/(Mo, W)S2Gray4-123400-38000.15700˚C/1292˚F1024˚C/1875˚F
Data generated from lab samples. Characteristics may vary depending on customer’s material, surface condition and part geometry.

Typical Applications for TD Coatings

  • Extrusion Punches & Dies
  • Perforating Punch
  • Burring Punch
  • Shaving Punches
  • Embossing Rolls
  • Coining Punches & Dies
  • Draw Punches & Dies
  • Knurling Tools
  • Bending Dies
  • Forming Dies
  • Hot Forging Dies
  • Powder Compaction Dies
  • Wire Draw Plugs
  • Tube Mandrels
  • Die-Casting Molds & Cores


TD Coatings Example

TD Coatings Example