HTS Coatings — machining & grinding

Colmonoy 69

16.5% Cr, 5% Mo, 4.5% Si, 3.8% B, 3% Fe, 2.1% Cu, 0.55% C, Ni-balance

  • Flame
  • HVOF
  • PTA

Colmonoy 69 is the corrosion-resistant Colmonoy — step up when wet chemistry is the driver. Same self-fluxing Ni-Cr-B-Si backbone Wall Colmonoy has built for sixty years, with 3% molybdenum and 2% copper layered in. Those two additions are the whole point: in acidic, chloride-bearing, and mildly aggressive aqueous service, 69 out-corrosion-resists standard Colmonoy 6, 56, and 88 by a meaningful margin, without giving up self-fluxing behavior or nuclear qualification. Hardness lands at 58-63 HRC across 69SC and 69SM (flame Spray-and-Fuse) and 69HV (HVOF); hot hardness holds HRC 49 through 1,000°F.

The flagship job is nuclear valve stems. Nickel-base hardfacings activate at roughly 1/265 the dose rate of cobalt-base Stellite, so BWR and PWR primary-circuit internals — gates, plugs, seats, stems, grid plates — spec Colmonoy-family chemistry to keep operator exposure down. Beyond nuclear, 69 is the pick for chemical-process pump sleeves, pharmaceutical wet-process equipment, marine tail-shaft liners, and any part in mildly corrosive plus abrasive service.

It costs more than Colmonoy 6 and is slightly softer than Colmonoy 88 — accepted trade-offs when corrosion is the failure mode. HTS runs it on Flame Spray-and-Fuse, HVOF, and PTA.

Got a chemical-service pump, valve stem, or marine shaft fighting wet chemistry? Send us a sketch — we'll scope the right process and quote it back.

Technical data

Hardness
~650-770 HV equivalent (HRC 58-63 conversion); fine-grained chromium-carbide and Ni-B-Si eutectic structure with well-distributed floret-shape primary borides at higher cooling rates
Hardness (HRC)
58-63 HRC as-deposited — consistent across spray-and-fuse (69SC, 69SM via J-3 Spraywelder / Fusewelder) and HVOF (69HV / JP 5000) per Wall Colmonoy TDS; hot hardness holds HRC 57 at 600°F (315°C), 54 at 800°F (425°C), 49 at 1000°F (540°C), 45 at 1200°F (650°C)
Bond strength
>13,000 psi (>90 MPa) bond strength HVOF (69HV, JP 5000, >0.060" thickness) per Wall Colmonoy TDS Table 5; Spray-and-Fuse deposits (69SC/69SM) are metallurgically bonded (substrate-limited) with true fusion interface at ~1,890°F / 1,030°C
Max service temp
~1,000°F continuous with useful hot hardness (HRC 49); particle-erosion service demonstrated up to 1,500°F in HVOF form (69HV); hardness still HRC 45 at 1,200°F
Max service temp
~540°C continuous; 815°C particle-erosion limit (HVOF); full hot-hardness curve characterized to 650°C
As-sprayed porosity
<2% HVOF (69HV, as-sprayed ≥98% dense); Spray-and-Fuse deposits essentially fully dense after fuse cycle (metallurgical bond, very low porosity)
Typical thickness
HVOF 69HV >60 mils demonstrated (>1.5 mm); Spray-and-Fuse 20-60 mils typical; PTA 40-120 mils (1-3 mm)
Melting range
Furnace fusing point ~1,890°F per Wall Colmonoy TDS Table 1
Density
8.06 (0.291 lb/in³) per Wall Colmonoy TDS Table 1

Where it earns its keep

  • Molybdenum (3%) plus copper (2%) additions dramatically improve corrosion resistance versus standard Colmonoy 56 / 6 / 88 in acidic, chloride, and wet-chemistry service — the differentiator of the Colmonoy 69 chemistry
  • Self-fluxing (B + Si scavenge oxides during fuse) — no separate flux, no shielding gas on the fuse step, true metallurgical bond after fuse cycle
  • Three-process flexibility: flame Spray-and-Fuse (69SC), coarser oxidizing-flame grade (69SM), and HVOF (69HV) on the shelf; PTA available through Wall Colmonoy's PTA program
  • Classic nickel-base hardfacing for nuclear specs — dose-rate inventory of cobalt-free Ni-Cr-B-Si alloys is roughly 1/265 that of Co-base Stellite grades, and Colmonoy-family alloys are well-qualified in BWR/PWR valve, grid-plate, and fast-breeder components
  • Extended plastic range above fuse temperature eliminates sagging and running on large or non-horizontal surfaces — a meaningful advantage over Colmonoy 6 on big parts
  • Hot hardness holds HRC 49 to 1,000°F — useful continuous wear service in chemical and power applications where WC-Co decarburizes
  • 69HV is a legitimate chromium-plate replacement — ≥98% dense, >13,000 psi bond, crack-resistant, and machinable with CBN or grindable with SiC/diamond

Where it doesn't

  • Slightly lower hardness than Colmonoy 88 (58-63 HRC vs. 59-64 HRC) — if abrasion is the dominant mode and the chemistry is benign, Colmonoy 88 is cheaper wear-per-dollar
  • Higher cost than standard Colmonoy 6 — the Mo + Cu chemistry carries a raw-material premium; specify it only when wet-chemistry corrosion is the design driver
  • Service temperature still capped at ~1,000°F continuous — not the right pick for sustained hot service; step up to Colmonoy 686 or Hastelloy overlay for high-temp corrosion
  • Weld and fusion are crack-sensitive on hardenable substrates — preheat, interpass control, and slow cool per Wall Colmonoy class table are mandatory
  • Do not apply to steels requiring post-fusion hardening and tempering — martensite formation will crack the deposit per TDS
  • Machining is difficult — CBN tooling (GE BZN compacts, Kennametal CNMA 433KC-210) preferred; finishing is typically by silicon-carbide or diamond grinding
  • Like all self-fluxing alloys, the fuse cycle (~1,890°F) must be survivable by the base part without distortion or metallurgical damage

Typical applications

  • Nuclear reactor valve stems, gates, plugs, and seats (classic cobalt-free hardfacing spec; dose rate ~1/265th of Co-base Stellite per published nuclear work)
  • Chemical-process pump sleeves, shafts, wear rings, and casings in acidic and chloride-bearing streams
  • Pharmaceutical and wet-process equipment requiring combined corrosion tolerance and abrasion resistance
  • Marine pump parts — tail shaft liners of tow boats, propeller shafts, bearing sleeves (per TDS application imagery)
  • Petrochemical gate valves, ball valves, and centrifugal pump internals (69HV HVOF for non-point-loading service)
  • Heat-exchanger tubes, tubesheets, and other parts exposed to mildly corrosive plus abrasive fluid service
  • Pulp-and-paper bed knives and chipper segments
  • Mixer and rotor blades in chemical reactors
  • Food-grade and sanitary pump components where nickel base is preferred over cobalt
  • Chromium-plating replacement (69HV) where density ≥98% and crack resistance matter over maximum hardness

Wear modes addressed

  • Low-stress and high-stress abrasion (fine chromium carbides and Ni-B-Si eutectics resist scouring)
  • Particle erosion up to ~815°C / 1,500°F in HVOF form (69HV)
  • Slurry and silt erosion in chemical-process and marine streams
  • Aqueous corrosion in acidic and chloride-bearing environments (Mo + Cu additions expand pitting and crevice resistance vs. standard Ni-Cr-B-Si chemistry)
  • Mild oxidation and hot-gas exposure to moderate temperatures (<650°C)
  • Adhesive and metal-to-metal sliding wear on non-point-loading contact surfaces
  • Galling in valve-stem service

Industries

  • Nuclear power generation (BWR and PWR valve internals, grid plates, fast-breeder reactor components)
  • Chemical and petrochemical process (acidic-service pumps, valves, heat exchangers)
  • Pharmaceutical and bio-process wet equipment
  • Marine (tow-boat tail shafts, propeller shafts, pump sleeves)
  • Oil and gas (corrosive-well pump internals, gate valves, ball valves)
  • Pulp and paper (bed knives, chipper segments, digester internals)
  • Food and beverage (sanitary pump and valve components)
  • Power generation (balance-of-plant valves and pumps in corrosive circuits)

Substrates

  • Low-carbon steels (<0.25% C) — apply without special precautions per TDS
  • Grey cast iron, Meehanite, malleable, ingot and wrought iron
  • Nickel base metals: nickel, Monel 400, Inconel 600, Nichrome, Chromel
  • Medium- and high-carbon steels (>0.25% C) — require controlled slow cooling in Sil-O-Cel, mica, or equivalent insulation
  • Stainless steels (304, 316, 316L, 316LN, 410, 420) — common nuclear/chemical substrate
  • Avoid on ferrous metals requiring subsequent hardening and tempering (martensite dimensional change will crack the deposit per TDS)
  • Hardenable base metals may be overlaid but must be isothermally annealed after uniform austenitizing

Which process, when?

Flame Spray-and-Fuse (grades 69SC fine and 69SM coarser-oxidizing) is the Wall Colmonoy-native route — powder deposited with a J-3 Spraywelder or Fusewelder torch, then torch-, induction-, or furnace-fused at ~1,890°F / 1,030°C to form a metallurgical bond. Chosen for uniform coverage over broad areas on parts that can take the fuse cycle; the extended plastic range of the 69 chemistry lets us fuse large or non-horizontal surfaces without sagging — a real production advantage over Colmonoy 6. HVOF (grade 69HV, JP 5000 parameters published) skips the fuse step entirely — lays down ≥98% dense coatings with >13,000 psi bond strength directly. This is the choice when the part can't take fuse heat, when a chrome-plate replacement is the goal, or when as-sprayed corrosion resistance is needed immediately. PTA delivers thick, weld-bonded overlays (40-120 mils) on point-loaded valve seats, sleeves, and shafts where a fused machinable surface is required. Pick Spray-and-Fuse for broad fused coverage, HVOF for no-fuse/chrome-replacement duty, 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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