HTS Coatings — machining & grinding

Chrome Oxide

99% Cr₂O₃

  • Plasma

Chrome oxide is the hardest, smoothest ceramic we spray — and the one anilox-roll and seal-face shops keep asking us for by name. Pure Cr2O3, 99% chromia, laid down by atmospheric plasma spray on top of a corrosion-resistant bond coat, then ground and lapped to whatever finish the job needs.

On the Vickers scale it runs 900 to 1200 HV routinely — harder than hardened tool steel by a wide margin. Bond strength is 4,000 to 6,000 psi on steel; service temperature holds to about 1,000°F in dry wear service and 350-400°F once the environment turns chemically aggressive and the coating is sealed. Lapped anilox surfaces finish into sub-micron Ra territory, which is why Cr2O3 has been the flexographic and gravure standard for decades.

We use it for printing anilox rolls (laser-engraved after coating), paper-making and corrugating rolls, mechanical seal faces, pump sleeves and impellers in abrasive slurry, textile thread guides, wire-drawing capstans, and parts running in alkaline chemistry where a WC-Co or Stellite would corrode.

Two honest caveats: chromia is brittle — don't spec it for impact. And finishing requires diamond wheels, so plan the cost and lead time. For everything else in its wheelhouse, nothing else in the ceramic family touches it.

Got an anilox, a seal face, or a slurry pump eating itself? Send us the print and the service conditions — we'll tell you if chrome oxide is the right answer.

Technical data

Hardness
900-1200 HV300 typical APS; ~1215 HV on combustion-sprayed Rokide C; up to ~1300 HV on optimized APS
Hardness (HRC)
62-72 HRC depending on formulation (62-70 HRC HTS spec; 65-72 HRC A&A spec)
Bond strength
4,000-6,000 psi on steel (APS); 4,545 psi on Rokide C combustion rod spray; Cr2O3-SiO2 composites reach 6,000 psi
Max service temp
1000°F for abrasive wear service; 350-400°F in corrosive chemical environments when properly sealed
Max service temp
540°C wear service; 177-205°C sealed corrosive service
As-sprayed porosity
<2% on dense sintered-powder APS (anilox grade); up to 5% on standard APS; 8.4% total porosity on combustion rod spray (Rokide C)
Typical thickness
3-25 (75-640 µm); >30 mils possible on cylindrical ODs without spalling, but 25 mil is the practical upper limit
Surface finish (Ra)
350-550 µin RMS as-sprayed; 15-35 µin diamond-ground; 5-8 µin superfinished; sub-micron Ra achievable on lapped/polished anilox surfaces

Where it earns its keep

  • Highest hardness in the common oxide-ceramic thermal-spray family — 900-1200 HV routinely, up to 1300 HV on optimized APS — translating to extreme abrasion and sliding-wear resistance
  • Finishes to sub-micron Ra when lapped or superfinished, which is why Cr2O3 is the de-facto anilox-roll and mechanical-seal face coating
  • Chemically inert against alkaline solutions and most mildly acidic media; sealed coatings hold up through 30-day immersion across pH 0-10 with no loss of wear resistance
  • Self-mating and anti-galling — two Cr2O3 faces running against each other resist pickup and scoring better than metallic mating pairs
  • Takes laser engraving cleanly at micron-scale cell geometry, making it the industry-standard surface for flexographic and gravure printing rolls
  • Non-conductive (dielectric) and optically near-black, useful in precision equipment and optical-absorbing applications

Where it doesn't

  • Brittle — chromia is a ceramic, so point-loaded impact or edge loading chips the coating; specify Cr2O3 for sliding, erosive, and corrosive duty, not impact
  • Diamond-only machining — Vickers hardness above carbide grinding wheels means finishing requires diamond grinding and lapping, which adds cost and cycle time versus metallic coatings
  • Temperature ceiling of ~540°C for wear service and ~200°C for sealed corrosive chemical service; for higher-temperature wear, step over to Cr3C2-NiCr
  • Porosity is real — standard APS runs 2-5%, which is why sealing (epoxy, aluminum phosphate, or polymer impregnation) is specified for aggressive chemical environments
  • Thickness limited to roughly 25-30 mils on cylindrical work before residual stress risks spalling; do not spec chromia for heavy build-up restoration

Typical applications

  • Flexographic and gravure anilox rolls (laser-engraved cell structures)
  • Paper-making and corrugating rolls
  • Mechanical seal faces (self-mating, anti-galling)
  • Pump sleeves, shafts, impellers, and end plates in abrasive slurry service
  • Textile machinery thread guides, capstans, and fiber-contact components
  • Wire drawing capstans, draw blocks, sheaves, and pulleys
  • Valve stems, ball valves, and oil seals exposed to alkaline or mildly acidic media
  • Food-processing sealing surfaces and heat-seal bars/jaws
  • Plastic mixing and extruder components resisting abrasive polymer compounds

Wear modes addressed

  • Low- and high-stress abrasion
  • Particle erosion (dry and low-angle)
  • Cavitation erosion in pump and valve service
  • Adhesive sliding wear and galling against metallic counterfaces
  • Sliding wear against hard counterfaces at sub-micron finishes
  • Chemical corrosion in alkaline and mildly acidic media (when sealed)

Industries

  • Printing (flexographic and gravure anilox rolls)
  • Pulp & paper (press rolls, doctor blade surfaces, corrugating rolls)
  • Textile (fiber-contact rolls, guides, spindles)
  • Chemical process (mechanical seals, pump internals, alkaline service)
  • Food processing (sealing surfaces, heat-seal jaws)
  • Wire and cable manufacturing (drawing capstans and blocks)
  • Pump and valve OEM/MRO
  • Power generation (auxiliary pumps and seals)

Substrates

  • Carbon and low-alloy steels (1018, 1045, 4140)
  • Stainless steels (304, 316, 410, 17-4 PH)
  • Cast iron (with appropriate bond coat)
  • Ni-base alloys for high-temperature pump and seal service
  • Aluminum and copper alloys (with NiAl or NiCr bond coat)

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.

Thinking about Chrome Oxide for a part?

Send us the spec or a photo. We'll tell you whether this fits, or point you at a better material for the job.

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