HTS Coatings — machining & grinding

Colmonoy 88

17% W, 15% Cr, 4% Si, 3.5% Fe, 3% B, 0.8% C, Ni-balance

  • Flame
  • HVOF
  • PTA

Colmonoy 88 is the highest-hardness self-fluxing alloy Wall Colmonoy makes — nickel-base, with 17% tungsten and 17% chromium carrying fine bi- and tri-metallic borides and carbides through a Ni-Cr-B matrix. Spray-deposited and fused, it lands at 59-64 HRC and holds hardness through 1,000°F continuous. HTS runs it on all three Wall Colmonoy processes we run: flame Spray-and-Fuse, HVOF, and PTA.

The reason to pick it over a cobalt-base Stellite comes down to three things. First, chemistry: nickel beats cobalt in mildly acidic and food-contact service, and cobalt pricing is volatile. Second, abrasion: at 59-64 HRC Colmonoy 88 is roughly twenty Rockwell points harder than Stellite 6, which shows up directly in dry-sand and slurry-erosion life. Third, microstructure: the hard phases are precipitated at 5-10 µm spacing, not blended as coarse WC grains, so slurry and silt can't find soft pockets between carbides. Where it loses to Stellite is impact — 3 ft-lb Charpy notched means don't pound it.

Glass-mold plungers, frac-pump plungers, extrusion screws, slurry-pipe elbows, petroleum gate valves and pump sleeves — if the duty is abrasion first, moderate heat second, mild corrosion third, Colmonoy 88 earns the job.

Got a worn plastic screw, a sand-pump housing, or a glass plunger due for rework? Send us a sketch — we'll scope the right process and quote it back.

Technical data

Hardness
~675-775 HV equivalent (HRC 59-64 conversion); hot hardness HRC 62 at 315°C/600°F, HRC 61 at 425°C/800°F, HRC 56 at 540°C/1000°F, HRC 43 at 650°C/1200°F per Wall Colmonoy Spray-and-Fuse data
Hardness (HRC)
59-64 HRC as-deposited (88F/88B/88C/88SA/88M spray-and-fuse, 88P1/P2 PTA, 88H HVOF); 55-60 HRC for the modified 88R-H grade with improved ductility
Bond strength
>13,000 psi (>90 MPa) HVOF as-sprayed; spray-and-fuse deposits are metallurgically bonded (substrate-limited) with a true fusion interface at ~1065°C/1950°F
Max service temp
~1,000°F continuous with useful hot hardness (HRC 56); erosion protection demonstrated up to 1,500°F (HVOF); glass-mold plungers run against molten silica at 1,800°F
Max service temp
~540°C continuous; 815°C particle-erosion service (HVOF); 982°C demonstrated in glass-mold plunger service
As-sprayed porosity
<2% HVOF (88H); fused spray-and-fuse deposits essentially fully dense (metallurgically bonded, very low porosity); HVOF density ≥98%
Typical thickness
Spray-and-fuse 20-60 mils typical; HVOF >60 mils demonstrated (>1.5 mm); PTA 40-120 mils (1-3 mm)
Melting range
~2,020°F (melting point); fusing temperature ~1,950°F (1,065°C)
Density
9.89

Where it earns its keep

  • Highest hardness in Wall Colmonoy's self-fluxing portfolio (59-64 HRC) — outperforms two-phase NiCrSiB+WC blends in slurry erosion because the hard phases are precipitated uniformly through the matrix, not coarsely blended
  • Fine 5-10 µm bi- and tri-metallic borides and carbides give superior finishing characteristics — grinds to a mirror-like sub-10 Ra surface
  • Metallurgical bond after fusing (spray-and-fuse, PTA) — true fusion interface, not mechanical adhesion
  • Hot hardness holds at HRC 62 to 600°F and HRC 56 to 1,000°F — useful continuous service where WC-Co decarburizes
  • Nickel base offers corrosion tolerance cobalt-base Stellites don't — better fit for mildly acidic and food-contact service
  • One alloy family, three processes: Flame (Spray-and-Fuse), HVOF, and PTA grades are on the shelf at HTS

Where it doesn't

  • Crack-sensitive on weld and fusion — preheat, interpass control, and slow cool per Wall Colmonoy class table are mandatory; thick sections on hardenable base metals require isothermal anneal
  • Low impact toughness compared to cobalt-base Stellites (Charpy 3 ft-lb notched) — not the pick for high-impact pounding service
  • Fusing temperature ~1,950°F means the base part has to survive that thermal excursion without distortion or metallurgical damage
  • Dilution control matters on PTA deposits — too much iron pickup drops hardness and abrasion life
  • Do not apply to steels requiring subsequent hardening and tempering — martensite dimensional change will crack the deposit
  • Machining is difficult with carbide tooling (CBN recommended); finishing is usually done by silicon-carbide or diamond grinding

Typical applications

  • Plastic-extrusion and injection-molding screw flights (single and twin-barrel)
  • Glass-mold plungers and forming surfaces against molten silica at ~1,800°F
  • Petroleum gate valves, ball valves, pump sleeves, pump shafts, bushings, wear rings
  • Frac-pump and triplex/duplex pump plungers; compressor rods and thermowells
  • Sand-pump and slurry-pump components; centrifugal pump parts
  • Slurry-pipe elbows, coal-discharge chutes, hydro-transport liners
  • Centrifuge scrolls, screw conveyors, and auger flight leading edges
  • Food-processing screw conveyors and handling surfaces (nickel base, mildly acidic service)
  • Heat-exchanger tubes and components requiring combined wear and corrosion service
  • Chrome-plating replacement where density (≥98%) and crack resistance matter

Wear modes addressed

  • High-stress and low-stress abrasion (fine hard phases 5-10 µm resist scouring)
  • Slurry and silt erosion — matrix-spacing smaller than erodent particle diameter
  • Particle erosion up to ~815°C/1,500°F in HVOF form
  • Three-body abrasion from dry particulates and aggregate
  • Metal-to-metal sliding wear on non-point-loading contact surfaces
  • Mild corrosion in petroleum and mildly acidic process streams (Ni-Cr matrix)
  • Hot gas and oxidation to moderate temperatures (<650°C)

Industries

  • Plastics processing (extrusion, injection molding, compounding)
  • Petroleum (upstream drilling tools, pump internals, frac equipment)
  • Glass container and forming
  • Pulp and paper
  • Mining and mineral processing (slurry transport, coal handling)
  • Power generation (pump and valve components)
  • Food and beverage processing (nickel base favored over cobalt for wash-down service)
  • Construction aggregate and cement (chutes, liners)

Substrates

  • Low-carbon steels (<0.25% C) — apply without special precautions
  • Grey cast iron, Meehanite, malleable, ingot and wrought iron
  • Medium-carbon and alloy steels (4140, 4340) — requires controlled slow cooling in Sil-O-Cel, mica, or equivalent insulation
  • Stainless steels (304, 316, 410, 420) — verify preheat/interpass per Wall Colmonoy class table
  • Nickel alloys (Monel 400, Inconel 600), Nichrome, Chromel
  • Avoid on metals requiring post-fusion hardening and tempering — martensite formation will crack the deposit

Which process, when?

Flame Spray-and-Fuse (grades 88F, 88B, 88C, 88SA, 88M) is the Wall Colmonoy-native process — powder is deposited with a Spraywelder or Fusewelder torch, then torch-, induction-, or furnace-fused at ~1,950°F to form a metallurgical bond. Ideal for uniform coverage over broader areas on parts that can take the fuse cycle. HVOF (grade 88H / 88R-H) skips the fuse step — it lays down ≥98% dense coatings with >13,000 psi bond strength directly, chosen when the part can't take fuse heat or when a chrome-plate replacement is the goal. PTA (grades 88P1, 88P2) is the answer for thick, weld-bonded overlays on point-loaded wear surfaces where 40-120 mils of fused, machinable hardfacing is needed. Pick spray-and-fuse for broad coverage, HVOF for no-fuse/replacement service, PTA for thick fused 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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