HTS Coatings — machining & grinding

Wallex 50

10% W, 19% Cr, 0.8% C, 2% Fe, 3.4% B, 2.8% Si, 18% Ni, 44% Co

  • Flame
  • HVOF

Wallex 50 is the middle of Wall Colmonoy's Wallex range — a self-fluxing cobalt-nickel hardfacing alloy nominally Co 45 / Cr 19 / Ni 18 / W 10 / B 3.4 / Si 2.8 / C 0.8 / Fe 1-2. It sits where pump, valve, and general-hardfacing jobs live: harder and more heat-tolerant than Wallex 6 (38-46 HRC), less aggressive than the impact-tuned Wallex 20 family, and blended for the mix of mild corrosion and red-hardness that a cobalt-only Stellite won't quite cover.

At 56-61 HRC (roughly 615-720 HV) with a 9.10 g/cc density, Wallex 50 fuses at ~2,000°F and holds useful wear performance through the ~1,500°F range where nickel Colmonoys are already softening. The boron-and-silicon self-fluxing chemistry means flame-sprayed deposits finish metallurgically bonded and sub-1% porosity after a fuse cycle — no separate flux. Nickel at 18% widens corrosion tolerance over straight-Co Stellites; tungsten at 10% builds the carbide/boride network for sliding, erosion, and cavitation.

We run it via Flame spray + fuse and HVOF for pump sleeves, valve trim, boiler-feed pump parts, mechanical seals, printing rolls, glass-mold tooling, and bushing/cam wear surfaces — then grind to print. Cobalt plus nickel carries a binder premium, so it earns its spot when corrosion and temperature both matter. Got a worn pump part? Send us a sketch.

Technical data

Hardness
~615-720 HV equivalent to the 56-61 HRC range (standard ASTM E140 conversion); specific HV values vary with process and finish
Hardness (HRC)
56-61 HRC as-deposited (Wall Colmonoy datasheet)
Bond strength
Metallurgically bonded after the fuse cycle (Spraywelder + Fusewelder) or when deposited by PTA — substrate-limited, not coating-limited; as-sprayed HVOF without a fuse step is a dense mechanical bond typical of HVOF Co-Cr-W alloys
Max service temp
~1,500°F useful red-hardness service (cobalt matrix retains hot hardness well above nickel-only alloys); short excursions higher with oxidation penalty
Max service temp
~815°C useful red-hardness service
As-sprayed porosity
Flame spray unfused 3-8%; after fuse cycle <1%; HVOF ~1%; PTA ~0%
Typical thickness
Flame spray + fuse 15-40; HVOF 5-20; PTA 40-120 (1-3 mm); finished by grinding
Melting range
~1,900-2,000°F (fusing temperature 2,000°F / 1,090°C per Wall Colmonoy datasheet)
Density
9.10

Where it earns its keep

  • Self-fluxing — boron and silicon scavenge oxides during the fuse cycle, so flame-sprayed deposits finish metallurgically bonded and dense without a separate flux or shielding gas
  • Cobalt matrix delivers genuine red hardness — holds useful wear resistance through roughly 815°C / 1,500°F where Ni-only Colmonoys are already softening
  • Nickel addition (18%) widens corrosion tolerance compared to straight cobalt Stellites, which matters in chemical and oil-and-gas fluids
  • Tungsten (10%) plus chromium borides build a hard carbide/boride network for sliding, erosion, and cavitation wear
  • Low coefficient of friction — specifically positioned for metal-to-metal contact in bushings, cams, and knife edges
  • Process-flexible: Flame spray + fuse, Spraywelder/Fusewelder, HVOF, and PTA all supported on one alloy
  • Machinable by grinding for a Co-base alloy at this hardness level

Where it doesn't

  • Cobalt raw-material pricing is volatile — expect materially higher cost per pound than Colmonoy 6 or other Ni-only self-fluxing alloys
  • Ni + Co binder premium: costs more than straight-cobalt Stellite 6 and more than every Colmonoy grade — spec it when the dual corrosion + red-hardness profile actually earns the price
  • For pure abrasion without a corrosion or temperature driver, Stellite 6 or Colmonoy 6 usually gives equivalent service at lower cost
  • Not an impact alloy — low coefficient of friction and hard boride network mean heavy shock loading can chip the deposit
  • Weld and PTA deposits are crack-sensitive; preheat, interpass control, and slow cool are standard
  • Flame-sprayed deposits must be fused before real service — as-sprayed is porous and mechanically bonded only

Typical applications

  • Pump sleeves, shafts, impellers, wear rings, and bearings in oil & gas and chemical process service
  • Valve trim, seats, and stems in mildly corrosive and high-temperature service
  • Boiler-feed pump components exposed to flashing hot water
  • Mechanical seal faces and seal sleeves
  • Printing roll components and paper-mill roll surfaces
  • Glass-manufacturing tooling (plungers, neck rings, shear blades) where red hardness matters
  • Bushings, cams, and knives where metal-to-metal sliding meets mild corrosion
  • Mining and mineral-processing slurry-pump parts
  • Hydro-power components (runners, seal rings) exposed to silt-laden water

Wear modes addressed

  • Metal-to-metal adhesive wear / galling (low coefficient of friction)
  • Low-stress abrasion and silt erosion
  • Cavitation and particle erosion in pump and valve service
  • Mild aqueous corrosion in oxidizing and reducing fluids
  • Hot oxidation and hot corrosion to roughly 815°C
  • Fretting at loaded contacts

Industries

  • Oil & gas (upstream and refining)
  • Chemical and petrochemical process
  • Pump and mechanical-seal OEM/MRO
  • Valve manufacturing and rebuild
  • Pulp, paper, and printing
  • Glass container and tableware manufacturing
  • Power generation (boiler-feed pumps, hydro)
  • Mining and minerals processing
  • Food and beverage process equipment

Substrates

  • Carbon and low-alloy steel (1018, 1045, 4140)
  • Martensitic stainless (410, 420, F6NM)
  • Austenitic stainless (304, 316, 316L)
  • Tool and die steels with controlled preheat
  • Nickel-base alloys (Inconel 600, 625) for elevated-temperature trim
  • Cobalt-base substrates for repair and rebuild

Which process, when?

Flame spray + fuse (Spraywelder / Fusewelder) is Wall Colmonoy's traditional Wallex 50 route — a 15-40 mil self-fluxing layer laid down with oxyacetylene, then fused at ~2,000°F so boron and silicon scavenge oxides and the deposit finishes metallurgically bonded at <1% porosity. HVOF is the answer when the part can't accept a fuse cycle or when you need a dense, sub-1% porosity thermal-sprayed coating at 5-20 mils on pump sleeves, impellers, or valve trim. PTA welding delivers the thickest, lowest-dilution deposits — 40-120 mils for valve trim, seat rings, and rebuild work that must survive thermal cycling. Pick flame spray + fuse for cost and coverage, HVOF for thin-and-dense on heat-sensitive parts, PTA for thick-and-bonded on cycling service.

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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