Stellite vs Tungsten Carbide Coating: How to Choose the Right One

Stellite vs Tungsten Carbide Coating: The Quick Answer

Stellite vs tungsten carbide coating comes down to failure mode, not hardness. Tungsten carbide (WC-CoCr, applied by HVOF or D-Gun) is the harder coating — 1,200-1,350 HV by HVOF, up to roughly 1,400 HV by D-Gun — and is the standard choice for abrasive and sliding wear at moderate temperature. Stellite (a cobalt-chromium-tungsten alloy, thermal-sprayed or weld-overlaid) is considerably softer, typically 350-470 HV (35-47 HRC) as-sprayed, but resists galling, cavitation and combined wear-corrosion at elevated temperature in a way tungsten carbide was never designed to.

If the component's problem is hard-particle abrasion or dry sliding wear, specify WC-CoCr. If the problem is two metal surfaces seizing or tearing against each other under load — valve seats, pump wear rings, high-temperature fasteners — or the environment combines heat with corrosion, specify Stellite. Both are available as engineered coatings on our thermal spray technologies page.

What Each Coating Actually Is

Stellite is a family of cobalt-chromium alloys — typically 25-33% chromium, with tungsten or molybdenum and a small amount of carbon — where hardness comes from chromium- and tungsten-carbide particles dispersed through a tough, corrosion-resistant cobalt matrix. It doesn't rely on a heat-treated martensitic structure, so it doesn't soften with temperature the way hardened steel does. The common grades are Stellite 6 (general-purpose), Stellite 12 (higher carbide fraction, harder, less tough) and Stellite 21 (lower-carbon, more machinable). It's applied by plasma spray or HVOF for thinner, dimensionally controlled coatings, or by PTA/laser weld overlay for thicker, fully fused deposits. Full detail is in our Stellite coating guide.

Tungsten carbide coating (WC-Co or WC-CoCr) deposits tungsten carbide particles in a cobalt or cobalt-chromium metallic binder via HVOF or Detonation Spray (D-Gun), producing a dense, low-porosity, mechanically bonded coating whose hardness comes directly from the high volume fraction of hard carbide grains. See our tungsten carbide coating guide for the full process and property breakdown.

Side-by-Side Comparison

The table below summarises the properties that actually drive a Stellite-vs-tungsten-carbide decision. Read the wear-mechanism row before the hardness row — a harder coating is not automatically the better one once galling or cavitation is the failure mode.

| Property | Stellite (Co-Cr-W) | Tungsten Carbide (WC-CoCr) | |---|---|---| | Typical hardness | 350-470 HV (35-47 HRC) as thermal-sprayed | 1,200-1,350 HV (HVOF), up to ~1,400 HV (D-Gun) | | Dominant wear resistance | Galling, adhesive/self-mated wear, cavitation | Abrasive wear, hard-particle erosion, dry sliding | | Max practical service temperature | ~650-700°C | ~450-500°C before the carbide phase decarburises | | Corrosion/oxidation resistance | Excellent — high Cr content forms a stable passive oxide | Good, with Cr in the binder, but coating integrity degrades above ~500°C | | Typical application process | Plasma spray/HVOF (thin) or PTA/laser weld overlay (thick) | HVOF or D-Gun | | Typical bond strength | 60-80 MPa (HVOF) | 60-80 MPa (HVOF), >80 MPa (D-Gun) | | Typical porosity | <2% (HVOF) | <2% (HVOF), <1% (D-Gun) | | Typical duty | Valve seats/trim, pump wear rings, high-temp fasteners, oilfield tool joints | Pump shafts, hydraulic rods, valve stems, sleeves |

Everything in the table except temperature and wear mechanism is close to a wash or favours WC on paper. Those two rows are what should actually decide the specification.

Why Stellite Wins on Galling, Cavitation and Heat

Galling is an adhesive-wear failure: two metal surfaces in sliding or oscillating contact momentarily weld together at high-friction points and tear apart, roughening the surface and accelerating further seizure. Cobalt-based alloys resist this unusually well because cobalt's crystal structure shifts between face-centred-cubic and hexagonal-close-packed forms under mechanical stress, which reduces the adhesive pickup that causes galling in most steels and even in hard coatings run against themselves. A carbide coating, however hard, does not have this property and can gall badly in self-mated or metal-on-metal seating service.

The same high chromium content that gives Stellite its corrosion resistance also keeps it stable at elevated temperature — up to roughly 650-700°C — because its hardness comes from carbides in a matrix rather than a heat-treatable structure that softens as temperature rises. That combination of toughness, corrosion resistance and retained strength under repeated impact is also why Stellite holds up well against cavitation erosion, where a harder but more brittle carbide layer can micro-crack under the repetitive collapse of vapour bubbles at a pump impeller or valve trim surface.

Why Tungsten Carbide Wins on Abrasive and Sliding Wear

Within its temperature envelope, WC-CoCr is simply harder and denser than Stellite by a wide margin, and in straightforward abrasive or hard-particle sliding wear — where the failure mechanism is material being cut or ploughed away rather than surfaces seizing together — that hardness translates directly into longer wear life. This is why WC-CoCr, not Stellite, is the standard specification for pump shaft sleeves, hydraulic cylinder rods, and other close-tolerance sliding-contact components exposed to grit or particulate contamination at or near ambient-to-moderate temperature. It is also the usual hard-chrome replacement for these duties, since its wear resistance and corrosion resistance both exceed conventional hard chrome plating.

Applying Stellite to a pure abrasive-wear duty typically gives up wear life for no benefit — its galling and corrosion advantages aren't in play, so the job is paying for toughness it doesn't need instead of the hardness it does.

Cost Reasoning: Don't Choose on Powder Price Alone

Stellite powder and tungsten carbide powder are priced differently — cobalt-chromium-tungsten alloys and tungsten-carbide-cobalt powders both carry meaningful raw-material cost, and neither is a clearly "cheap" option, so cost differences between the two are usually smaller than the difference in wear life they deliver in the right application. The economics only make sense once the failure mode is identified correctly: putting WC-CoCr on a galling valve seat wastes money on a coating that will seize and fail early regardless of its hardness rating, while putting Stellite on an abrasive-wear shaft sleeve wastes money on toughness and corrosion resistance the application doesn't need, at the expense of the hardness that would have extended its service life.

The right way to model cost is per operating hour or per maintenance interval for the correct material, not per square metre of coating compared across the wrong material. For a specific component, duty cycle and failure history, contact us to get a quote and a material recommendation rather than guessing between the two.

Selection Checklist: Stellite or Tungsten Carbide?

Work through this checklist before finalising the specification. Where a component genuinely sees both galling and abrasive wear, share the full duty cycle with a coatings engineer rather than defaulting to either material.

• Primary failure mode is seizing, galling or adhesive wear between mating metal surfaces (valve seats, wear rings, fasteners) → specify Stellite
• Primary failure mode is abrasive or hard-particle wear against grit, sand or slurry (shaft sleeves, hydraulic rods) → specify WC-CoCr
• Component sees cavitation erosion (pump impellers, valve trim in throttling service) → Stellite's toughness and corrosion resistance generally outperform a harder but more brittle carbide layer
• Sustained or peak service temperature above ~500°C but below ~650-700°C → Stellite; above ~700°C, neither coating is appropriate and chromium carbide or a ceramic should be evaluated instead
• Component also faces aqueous, salt-spray or general chemical corrosion at moderate temperature → Stellite's high chromium content generally gives the stronger corrosion margin
• Duty is dry, moderate-temperature, particulate-laden sliding wear with no galling risk → WC-CoCr is the default and usually the more cost-effective choice
• Uncertain which failure mode dominates → send photos of the failed or worn part; wear patterns (torn/seized surfaces vs. scored/cut surfaces) usually identify the mechanism quickly

Common Mistakes When Choosing Between Stellite and Tungsten Carbide

These specification errors show up repeatedly in enquiries and are worth catching before a drawing goes out for quote.

• Specifying tungsten carbide on a metal-to-metal seating or sliding surface without checking for galling risk — a harder coating does not fix an adhesive-wear problem and can gall as badly as untreated steel
• Specifying Stellite on a pure abrasive-wear duty purely because it's a well-known "premium" coating — its lower hardness gives up wear life that WC-CoCr would have delivered for similar cost
• Comparing the two materials on hardness numbers alone — Stellite's 350-470 HV looks weak next to WC-CoCr's 1,200+ HV on a datasheet, but hardness isn't the property that predicts performance in galling or cavitation service
• Ignoring peak transient temperature and checking only the steady-state duty point — a component nominally at 400°C that spikes above 500°C during upset conditions needs Stellite's higher temperature margin, not WC-CoCr
• Treating both as generic "hard coatings" on a specification that doesn't name the material — this lets a coating shop substitute whichever is on hand, which may be entirely wrong for the actual failure mode

Get a Quote for Stellite or Tungsten Carbide Coating

Lotus Surface Tech is an ISO 9001:2015-certified thermal spray facility in Chennai, Tamil Nadu, operating since 2015, applying both Stellite and tungsten carbide (WC-Co, WC-CoCr) coatings by plasma spray, HVOF and Super-D-Gun on components up to Ø800 mm x 7 m, with in-house precision grinding to finished size. Our engineers review the actual failure mode — galling, abrasion, cavitation or corrosion — before recommending a material, so the specification matches how the part is actually failing rather than which coating happens to be popular.

Full process and capacity detail is on our technologies page. If you're specifying a new component or replacing a coating or plating that failed prematurely, contact us to get a quote — send the part drawing, the failure mode you're seeing in service, and the operating temperature and environment, and we'll recommend the right material.