Tribaloy T-400 is the specialist's pick for galling — a Co-Mo-Cr-Si alloy built around an intermetallic Laves phase instead of carbides. That microstructure is why it keeps showing up on diesel exhaust valve faces, sour-gas valve seats, downhole completion tools, and pump sleeves where metal-to-metal contact and marginal lubrication would chew up almost anything else. High molybdenum gives it sour-service and acidic corrosion resistance most Stellites can't match, and it holds useful hardness up through roughly 700°C in valve and steam duty.

At HTS we deposit T-400 by HVOF for thin, dense (<1% porosity) coatings on valve plugs, seats, and pump sleeves that can't take weld heat; by PTA when the part needs a thick, metallurgically-bonded overlay on a downhole tool or high-pressure valve; and by plasma spray where geometry or substrate constraints rule out HVOF. Preheat, interpass control, and slow cool are not optional on weld deposits — the Laves phase is brittle, and T-400 will crack if you rush it.

One honest caveat: T-400 is not an impact alloy. If your trim sees shock loading, specify Stellite 6 or 12. For galling, sour service, and high-temperature sliding wear, there's very little that beats it.

Got a valve or downhole tool eating itself alive? Send us a sketch — we'll spec the right T-400 process for the part.

Technical data

Hardness: 540-640 HV typical as-deposited; Laves-phase microhardness ~1000-1200 HV (particulate)
Hardness (HRC): 52-58 HRC typical HVOF/PTA deposits; broader reported range 44-58 HRC depending on process and dilution
Bond strength: HVOF ~10,000 psi (~70 MPa) on prepared steel; PTA weld overlay metallurgically bonded (substrate-limited)
Max service temp: ~1,290°F useful hardness retention in valve service; oxidation resistance to ~1,650°F in short excursions
Max service temp: ~700°C in valve/steam service; oxidation resistance to ~900°C short-term
As-sprayed porosity: <1% HVOF (typ. 0.3-0.8%); weld/PTA ~0%
Typical thickness: HVOF 5-20; PTA 40-120 (1-3 mm); plasma spray 10-25
Melting range: 2354-2444°F
Density: 8.6-8.9

Where it earns its keep

Self-lubricating via Laves intermetallic — exceptional galling resistance without carbides
Outstanding corrosion resistance in sour-gas, saltwater, and acidic service (high Mo + Cr)
Retains hardness and wear resistance to ~700°C in valve and steam service
Dense HVOF deposits run sub-1% porosity — suitable for cavitation and erosion in valve trim
Performs where lubrication is marginal or absent (boundary/no-lube contacts)
Applicable by plasma spray, HVOF, and PTA — multiple process paths for part geometry

Where it doesn't

Very brittle — the Laves phase that carries the wear resistance also cracks under impact; not suitable for shock loading
PTA and weld overlays are crack-sensitive; preheat, interpass control, and slow cool are mandatory
Grinding is tough — the hard Laves phase makes finishing slow and diamond wheels are typical
Expensive — high molybdenum + cobalt loading drives raw-material cost well above Stellite 6
For impact-tolerant valve trim, specify Stellite 6 or Stellite 12 instead — T-400 is a steady-state / no-impact alloy
Cobalt raw-material volatility affects lead time and pricing

Which process, when?

HVOF is the default when a sub-1% porosity coating is needed on a valve seat, plug, or pump sleeve that can't take weld heat — dense, well-bonded, and finished by grinding to print. PTA weld overlay is the right call for thick (40-120 mil), metallurgically-bonded deposits on downhole tools, high-pressure valve trim, and parts that will see thermal cycling — but preheat, interpass temp, and slow cool are not optional on T-400. Plasma spray suits thinner protective layers and more complex part geometry where HVOF line-of-sight is constrained. All three processes deliver the Laves-phase microstructure that defines T-400; process selection is driven by deposit thickness, substrate heat tolerance, and part geometry.

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.

Kennametal Stellite — Tribaloy T-400 and T-400C Alloys Technical Data
“Tribaloy family cobalt alloys consist of a hard intermetallic (Laves) phase dispersed in a softer matrix of eutectic or solid solution; developed for improved resistance to high-temperature wear, galling, and corrosion.”
MatWeb — Kennametal Stellite Tribaloy T-400 Cobalt Alloy
“Co-Mo-Cr-Si alloy; nominal 28.5% Mo, 8.5% Cr, 2.6% Si, Co balance; hardness typically 52-58 HRC; melting range ~1290-1340°C; density ~8.6 g/cm³.”
Ametek / Powderclad — Tribaloy T-400 Technical Datasheet
“T-400 contains hard intermetallic phases of Mo and Si providing excellent wear properties over a wide temperature range; recommended for valve seats, diesel exhaust valves, and components requiring galling resistance.”
ASM Alloy Digest Co-114 — Tribaloy T-400C Cobalt Hardfacing Alloy
“Cobalt hardfacing alloy developed for galling, corrosion, and high-temperature wear service; Laves-phase strengthened Co-Mo-Cr-Si composition.”
Valve Magazine — Hardfacing for Valves: Materials and Processes
“Tribaloy alloys are specified where galling resistance is the governing wear mode; Laves-phase microstructure carries the load in place of carbides.”
Deloro — Tribaloy T-400 Material Data Sheet
“Co-based Laves-phase alloy; HVOF and PTA deposits deliver dense coatings with outstanding galling resistance and retained hardness at elevated temperature.”

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.

Tribaloy T-400

Technical data

Where it earns its keep

Where it doesn't

Typical applications

Wear modes addressed

Industries

Substrates

Which process, when?

Sources

Thinking about Tribaloy T-400 for a part?