HTS Coatings — machining & grinding

Tungsten Carbide · Cobalt (83/17)

83% WC, 17% Co

  • HVOF
  • HVAF

Pick WC-17Co when the 88/12 keeps chipping. That's the whole argument. Same tungsten-carbide chemistry — same HVOF deposition — just a fatter cobalt binder (17% vs. 12%) that absorbs the shock instead of cracking under it.

We spray it the same way we spray the 88/12 workhorse: HVOF gun, supersonic flame, dense layer, ground and polished to the finish your part needs. You give up some hardness — typically 900 to 1100 HV on Vickers versus 1050 to 1350 for WC-12Co — and you get back toughness, ductility, and impact resistance. Bond strength stays up around 68 MPa on C633 pull tests. Porosity stays under 2%.

This is the coating for mud-motor rotors taking helical loading 400 hours at a time. It's the coating for vibrating-screen parts that eat rocks. Slurry pump impellers running mixed particulate. Crushing rollers. Valve trim that slams shut on abrasive slurry. Anywhere a WC-12Co deposit keeps spalling at the edges, the 17% grade holds.

Limits are the same as 88/12 — above 930°F the WC decarburizes; in wet acid or sour gas, specify WC-10Co-4Cr. For pure steady abrasion with no impact, WC-12Co still wins on wear rate.

If your 88/12 service life is shorter than your wear model predicted, the answer is probably 83/17. Tell us the part and the failure mode.

Technical data

Hardness
900-1100 HV300 typical HVOF; softer than WC-12Co (1050-1350 HV) by design — the extra 5% Co binder trades hardness for toughness
Bond strength
~9,900 psi (68 MPa) measured on HVOF WC-17Co per ASTM C633; HVOF/HVAF deposits routinely clear 10,000 psi threshold same as 88/12
Max service temp
930°F
Max service temp
500°C
As-sprayed porosity
~1-2% HVOF (measured 1.57% in MDPI comparison study); HVAF drops under 1%
Typical thickness
3-15 (75-380 µm) standard; production mud-motor rotors and pump parts commonly 200-500 µm
Surface finish (Ra)
90-120 as-sprayed; 2-4 diamond-ground; 1 superfinished (same post-processing profile as WC-12Co)

Where it earns its keep

  • Higher toughness and impact resistance than WC-12Co — the 17% cobalt binder absorbs shock the 12% grade spalls from
  • Better ductility and fracture toughness than 88/12; preferred when the duty cycle includes flex, vibration, or thermal cycling
  • Still very high hardness vs. any metallic overlay (Stellite, Inconel, hard chrome) — 900-1100 HV is well above 650-700 HV for hard chrome
  • Dense HVOF deposition with good bond strength (~68 MPa) and low open porosity; HVAF tightens the structure further
  • Same grind/superfinish path as WC-12Co — mirror Ra on sealing surfaces remains available
  • Documented service-life uplift over hard chrome on mud-motor rotors: Oerlikon Metco cites 10x improvement (80 to 800 service hours) for HVOF WC-Co vs. chrome plate

Where it doesn't

  • Lower hardness than WC-12Co means faster abrasive wear rate on pure-abrasion jobs — if the service is steady, particulate-only abrasion with no impact, specify 88/12 instead
  • Same 500°C / 930°F decarburization limit as WC-12Co — WC dissociates to W₂C and free W above that, softening the coating; step up to Cr₃C₂-NiCr for higher temperatures
  • Same corrosion limit as 88/12 — 17% cobalt binder is not for salt spray, wet acid, or sour-gas service; specify WC-10Co-4Cr when the environment turns chemically aggressive
  • Decarburization during spraying forms some W₂C and amorphous binder phases regardless of process tuning — this is inherent to HVOF WC-Co chemistry, managed by spray parameters
  • Softer than WC-12Co means sealing-surface life under pure sliding wear is shorter — specify 88/12 for hydraulic-rod and calendar-roll duties where impact is not part of the story

Typical applications

  • Mud-motor rotors and stator components where helical loading and LCF fatigue cycle the coating
  • High-impact valve trim and plug valves in slurry service with rocky or mixed particulate
  • Vibrating-screen components and crushing rollers exposed to repeated impact loading
  • Slurry pump impellers and backing plates in mixed-particulate erosion service
  • Extrusion dies and shrouds that see thermal cycling in addition to wear
  • Sucker-rod couplings and pump seals where flex and impact accompany the wear duty
  • Exhaust-fan blades and wear parts in power and process plants with particulate-laden gas

Wear modes addressed

  • Impact wear and hammer wear
  • Erosion by mixed or rocky particulate at variable angle
  • Thermal-shock-driven surface spalling
  • Sliding wear with shock loading
  • Fretting wear (lower fretting than WC-CoCr per Höganäs)

Industries

  • Oil & gas (downhole directional-drill mud motors, completions)
  • Mining and mineral processing (slurry pumps, vibrating screens, crushers)
  • Power generation (hydro-turbine components, exhaust fans)
  • Pulp & paper (select roll and pump duties with impact)
  • Steel and aluminum mills (rolls and fans)
  • Petrochemical and pump/valve (impact valve trim, plug valves)

Substrates

  • Low-alloy and medium-carbon steels (4140, 4340, 1045)
  • Stainless steels (17-4 PH, 410, 316)
  • Hydro-turbine steels (13Cr-4Ni martensitic stainless)
  • Nickel-base superalloys where ductile wear layer is preferred over 88/12
  • Titanium alloys where fatigue preservation matters (WC-17Co has been paired with shot peening on TC21)

Sources

Data points on this page draw on the following published references. Nothing here replaces a material-specific review by our process engineers — but it's the working starting point.

Material data on this page is provided as a general reference and can vary by lot, substrate, and application. Contact HTS to confirm the right material and specification for your specific part.

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