← All technical guides

Tungsten carbide in downhole tools: where it goes, and how to pick a grade

**Ask five suppliers for a "downhole carbide grade" and you'll get five different answers — because a downhole tool is not one wear problem, it's five. Each part fights a different enemy: abrasive sand, high-velocity erosion, impact, corrosion, or a mix. The part that tells you the grade is the failure mode, not the tool name.**

1. The problem

Downhole tools run thousands of meters below the wellhead in sand, brine, sour gas and heat. One tool body can carry several carbide components, each wearing by a different mechanism. Ordering them all in "the same hard grade" usually means some parts wear out early and some crack — the classic signs of a material picked by name instead of by mechanism.

2. The conclusion

Map the failure mode first, then the grade direction follows in one step:

Component	What kills it	Direction
ESP pump shaft bushings / sleeves	Abrasive sand cutting in rotating contact	Fine-grain, high-hardness cobalt grades (abrasive wells); switch to nickel binder in brine or acid wells
Choke/nozzle beans, flow nozzles **	High-velocity erosion at high pressure drop	Fine-grain, high-hardness grades; geometry (multi-stage) is the first fix at extreme ΔP; nickel binder for sour wells
Milling shoes / junk mills	Cutting through metal junk, casing and packers	Hard, wear-resistant for cutting edges; coarse grain helps survive interrupted cutting
Stabilizer / gauge protection inserts	Scraping wellbore + impact	Coarse-grain, high-toughness grades — this part chips more than it wears
Bridge plug / frac plug slips, packer slips	Gripping casing under load, sharp teeth break off	Toughness first: higher binder, coarse grain so teeth don't snap under shear + impact

** ESP sleeve and choke points are upstream of the pieces we quote — choke trim service itself is covered in our separate guide on writing a choke trim spec.

3. The basis

• **ESP bushings/sleeves:** ESPs spin fast (thousands of rpm) in sand-laden production fluid. Standard bushings erode first, then the shaft frets and the pump fails — a costly workover. Industry practice is tungsten carbide with a cobalt binder for abrasive wells and a nickel binder where brine or acid dominates. Hardness runs around 89–92.5 HRA. What separates a good part from a bad one is not the grade code — it's the finishing: mirror-ground bores (Ra ≤ 0.2 µm) and tight concentricity, because that is what controls heat and fretting at high rpm.
• **Slips and anchor teeth:** carbide slips for bridge plugs, frac plugs and packers grip the casing wall under load. Failure is usually tooth breakage, not wear — so the material is biased toward toughness (higher binder, coarse grain), the opposite of what a "wear" instinct would pick. This is the same logic as heavy-impact tooling.
• **Stabilizers and gauge pads:** these scrape the wellbore and take impacts. Coarse-grain, high-toughness grades resist the chipping. Fine-grain high-hardness grades here crack after welding or under shock.
• **Milling shoes:** cutting metal junk is a metal-removal job first — hard, wear-resistant grades hold the edge; a tougher variant survives interrupted cutting and shock.
• **Elevated temperature is always in the background** — downhole heat softens binder and accelerates corrosion. Low-temperature assumptions in grade selection don't transfer downhole.

Standards anchor: GB/T 18376 and ISO 513 classify grades and give comparability across suppliers. ISO 3327 (TRS) is the practical toughness indicator to put in the spec. No standard replaces the duty statement: media chemistry (H₂S, CO₂, brine), solids size and loading, rpm, temperature, and the failure history of the previous part.

4. The advice

• **Write the duty sheet, not the tool name.** "Bridge plug slip, 5-1/2" casing, 96 hr H2S exposure, impact at set" tells us more than any grade code.
• **Split the material if the tool splits the duty.** A mill body and its cutting inserts can honestly use two different materials. Don't force one grade over the whole tool.
• **Ask for finishing data on rotating parts.** For ESP sleeves the surface finish and concentricity are performance specs, not cosmetics.
• **Send a photo of the failed part.** A chipped tooth, a scoured bore and a leached surface each point to a different material direction — one photo usually settles it.

Send the drawing, the duty and — if you have it — the failed part. We'll map each component to a material direction and quote within 1–2 business days.

---