HTS Coatings — machining & grinding

Wallex 55

34.8% W, 12% Cr, 2.3% C, 1.2% Fe, 2% B, 1.7% Si, 12.6% Ni, 33.4% Co

  • HVOF

Wallex 55 is the high-tungsten flagship of Wall Colmonoy's Wallex family — a self-fluxing cobalt-nickel hardfacing alloy carrying roughly 35% tungsten, far more than any other standard Wallex grade. Where Wallex 50 sits at 10% W and trades some abrasion for balanced corrosion-wear duty, Wallex 55 pushes hard in the abrasion direction. The cobalt-nickel binder (~33% Co / ~13% Ni) keeps the hot-hardness and corrosion balance cobalt-only Stellites can't match in mildly acidic oil & gas service, and the boron-silicon self-fluxing chemistry lets HVOF deposits wet and bond without auxiliary flux. Hardness lands at 55-62 HRC — highest in the family.

HTS runs Wallex 55 almost exclusively via HVOF, with spray-and-fuse as the secondary process. The duty profile is narrow: extreme-abrasion pump and valve components in sand-laden oil & gas service, printing rolls carrying high-solids inks, slurry pump sleeves and impellers in hard-rock mining where Stellite 1 cracks and WC-CoCr has the wrong chemistry for the temperature window.

The trade-offs are honest — Wallex 55 is very expensive (high W + Co + Ni) and very crack-sensitive, so thin deposits only. For medium-grade wear, spec Wallex 50 every time.

Got a pump sleeve or choke trim eating through Wallex 50 or splitting Stellite 1? Send us the failed part — we'll scope whether Wallex 55 earns the cost.

Technical data

Hardness
~595-746 HV equivalent (HRC 55-62 conversion); HVOF microhardness readings commonly fall in the 650-750 HV range on dense, well-fused sections
Hardness (HRC)
55-62 HRC as-deposited (highest in the Wallex family); spray-and-fuse and HVOF deposits sit in the upper portion of this range when fused to metallurgical density
Bond strength
>10,000 psi (>69 MPa) typical HVOF as-sprayed on prepared substrates; spray-and-fuse deposits form a metallurgically bonded fusion interface (substrate-limited), not mechanical adhesion
Max service temp
~1,200°F continuous with useful hot hardness; cobalt-nickel binder gives meaningful oxidation resistance above most nickel self-fluxing grades
Max service temp
~650°C continuous; short-duration peaks higher depending on loading and atmosphere
As-sprayed porosity
<2% HVOF; fused spray-and-fuse deposits essentially fully dense (metallurgically bonded, very low porosity)
Typical thickness
Thin deposits only — 10-30 mils HVOF; 15-40 mils spray-and-fuse. Thick sections are discouraged because of crack sensitivity
Melting range
~2,000°F processing/fusing temperature (≈1,090°C), consistent with the Wallex 50 family
Density
~9.3-9.6 (elevated over Wallex 50's 9.10 g/cc due to higher tungsten content)

Where it earns its keep

  • Highest tungsten content in the Wallex family (~35% W) — delivers maximum abrasion resistance of any standard Wallex grade
  • Cobalt-nickel binder balances hot-hardness (cobalt contribution) with corrosion tolerance (nickel contribution) — a chemistry Stellite-class cobalt-only alloys can't match in mildly acidic service
  • Self-fluxing chemistry (B, Si) lets HVOF deposits wet and bond well — dense, low-porosity coatings without auxiliary flux
  • Metallurgical bond after spray-and-fuse — true fusion interface, not mechanical adhesion
  • Maintains meaningful hot hardness to ~650°C — outperforms WC-Co composites in oxidizing/temperature service
  • Fills the gap between Stellite 1 (cobalt-only, corrosion-limited in nickel-favoring service) and WC-CoCr (wrong chemistry for hot oxidizing environments)

Where it doesn't

  • Very expensive — high tungsten (~35%) plus cobalt (~33%) plus nickel (~13%) makes this one of the most material-cost-heavy hardfacing alloys on the shelf
  • Very crack-sensitive — thin deposits only are recommended; single-pass, multi-layer application with preheat and slow cool is mandatory. Thick sections almost always split
  • If medium-grade wear is the duty, specify Wallex 50 instead — you'll save significant material cost and avoid crack risk while still getting excellent abrasion and corrosion balance
  • Generally chosen only when Stellite 1 alternates or WC-CoCr aren't the right fit — don't default to Wallex 55; prove the need first
  • Low impact tolerance — not the pick for pounding or hammer-blow service; composite WC grades handle that better
  • Finish by grinding only — silicon-carbide or diamond wheels. Too hard for carbide tooling
  • Dilution control matters on any fused application — too much iron pickup drops hardness and abrasion life

Typical applications

  • Extreme-abrasion pump and valve components in oil & gas service (choke trim, ball valves, wear sleeves in sand-producing wells)
  • Printing rolls carrying high-solids and abrasive ink formulations where a thin, hard, smooth deposit is required
  • Slurry pump sleeves, wear rings, and impeller shrouds in hard-rock mining — taconite, copper-sulfide, gold tailings
  • Severe-service valve seats and gate wedges in solids-laden process streams
  • Expeller and worm surfaces in mineral-concentration and dewatering equipment
  • Thin-section hardfacing on parts where Stellite 1 cracks and WC-CoCr is the wrong chemistry

Wear modes addressed

  • Severe three-body abrasion (hard-rock ore, silica, sand)
  • Low-angle slurry erosion with solids-carrying fluids
  • High-stress gouging abrasion on valve and pump contact surfaces
  • Combined abrasion plus mild-to-moderate corrosion (cobalt-nickel binder tolerates more chemistry than cobalt-only grades)
  • Hot-hardness retention under continuous service — maintains cutting/wear edge where WC-Co would decarburize

Industries

  • Oil & gas (upstream drilling, pump internals, sand-service valve trim, frac equipment)
  • Hard-rock mining and mineral processing (slurry transport, tailings handling, dewatering)
  • Printing and coating (abrasive-ink rolls, high-solids pigment processing)
  • Pulp and paper (refiner and chipper wear parts in aggressive furnish)
  • Chemical processing (severe-service valves and pumps with abrasive solids)
  • Power generation (boiler-feed and ash-handling pump components)

Substrates

  • Low-carbon and medium-carbon steels (1018, 4140) — the workhorse pump and valve bodies
  • Martensitic stainless (410, 420) — valve trim and pump sleeves
  • Austenitic stainless (316, 316L) — oil & gas service with chloride exposure
  • Cast irons and nodular irons — with disciplined preheat and slow cool
  • Nickel alloys (Monel, Inconel 625) — specialty valve and pump components
  • Avoid on metals that must be post-hardened and tempered after coating — martensite dimensional change will crack the deposit

Which process, when?

HVOF is the primary process for Wallex 55 — dense, low-porosity, thin deposits (10-30 mils) on prepared substrates with >10,000 psi bond. The self-fluxing B/Si chemistry makes this material particularly well-suited to HVOF because the deposit wets and bonds without auxiliary flux, and the oxygen-limited flame keeps tungsten oxidation in check. Spray-and-fuse (flame deposit followed by torch, induction, or furnace fuse at ~2,000°F) is the traditional Wall Colmonoy process and yields a metallurgically bonded layer 15-40 mils thick — use it where the part can take the fuse cycle and a true fusion interface matters. PTA are rare on Wallex 55 because the alloy's crack sensitivity and high material cost make thick weld-bonded overlays hard to justify — in most cases, if PTA-thickness hardfacing is needed, Colmonoy 88 or a composite tungsten-carbide product is the better spec. Pick HVOF first, spray-and-fuse second; reach for a different alloy entirely before forcing a thick weld-bonded overlay.

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.

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