Stellite 6 Hardfacing on Gate, Globe and Butterfly Valves
Technical guide · Supreme Valves India · Updated 2026-10-28
Direct answer: Specify Stellite 6 (or equivalent cobalt hardfacing) on seating surfaces when steam, flashing condensate or erosive flow will wear soft or unfaced seats. Write the scope clearly — seat only, or seat and wedge/disc — because “stellited” alone is ambiguous on a BOQ.
Stellite language appears dozens of times in our RFQ archive: forged blowdown globes, API 600 gates, and WCB butterflies with “SS316 STELLITED” discs.
What gets hardfaced
| Valve type | Typical hardfaced parts | Common BOQ phrase |
|---|---|---|
| Gate (API 600 / 602) | Seat rings; sometimes wedge faces | FULL STELLITE SEAT AND WEDGE |
| Globe (blowdown / drain) | Seat and disc | SEAT IN-SITU STELLITED, DISC + STELLITE |
| Butterfly | Disc edge and/or seat | TRIM SS316 STELLITED |
When soft trim is not enough
- Continuous or intermittent boiler blowdown
- High ΔP steam drains and vents
- Flashing condensate across the seat
- Abrasive or high-cycle metal-seat butterfly service
For clean hydrocarbon isolation at Class 150 with infrequent cycling, Trim #8 without hardfacing is often enough. Do not add Stellite “just in case” without a duty reason — cost and lead time rise.
Stellite 6 vs “hardfaced”
Stellite 6 is the usual cobalt-chromium hardfacing alloy specified by name. Some specs say “hardfaced” or “HF” and allow equivalent overlays. Match the project welding/hardfacing procedure qualification if the ITP requires it. Body material stays carbon or stainless steel; only the seating skin is cobalt alloy.
RFQ wording that avoids disputes
- Alloy: Stellite 6 or approved equivalent
- Surfaces: seat rings / wedge / disc (list each)
- Integral vs welded-in seat rings
- Any NDE or hardness checks on the overlay
Use the Stellite trim RFQ page for packages, and pair forged blowdown tags with the A105 Class 800 globe RFQ.
Frequently asked questions
Does Stellite mean the whole valve is cobalt alloy?
No. Stellite usually means a hardfacing overlay on seating surfaces (seat rings, wedge faces, disc edges). The body remains WCB, A105 or stainless. State which parts are hardfaced on the RFQ.
Why do butterfly BOQs say TRIM SS316 STELLITED?
They typically want an SS316 disc with a hardfaced seating edge or mating seat for higher wear or temperature than a soft elastomer alone. Confirm whether the seat is metal/hardfaced or still resilient with a stellited disc.
Does hardfacing change delivery time?
Yes. Hardfacing, machining and any required NDE add days to weeks versus soft trim. Call it out early on steam and blowdown packages.