HTS Coatings — machining & grinding

Inconel 718

19% Cr, 19% Fe, 5% Nb, 3% Mo, Ni-balance

  • HVOF

Inconel 718 is the aerospace superalloy coating — the same nickel-chromium-iron-niobium chemistry (19% Cr, 19% Fe, 5% Nb, 3% Mo, Ni-balance) that makes up much of a modern jet engine's high-pressure section, sprayed back on as a repair deposit. Its defining trick: it's precipitation-hardenable after spray. Run a proper solution-anneal and double-age cycle (per AMS 5663, 1325°F / 1150°F) and fine γ′ + γ″ phases nucleate in the lamellae, driving microhardness from around 560 HV0.2 as-sprayed to nearly 700 HV0.1 aged. Restored dimensions and real superalloy mechanicals, not just a soft filler.

At HTS we apply 718 by HVOF for dense (<1.5% porosity) 10-60 mil build-ups on compressor blade tips, vane platforms, seal teeth, and shaft journals — the cold-section hardware that wears undersize long before the forging is scrap. The alloy does double duty in oil & gas sour service: subsurface safety valves, packers, and tubing hangers rated to 20,000 psi under API 6ACRA and NACE MR0175. Useful strength holds cryogenic-to-650°C, and the wrought-spec chemistry (UNS N07718, AMS 5662/5663) opens aerospace qualification pathways other thermal-spray alloys can't touch.

Blade tips worn below drawing? Sour-service valve body needing an overlay? Send the print and heat-treat spec — we'll scope the HVOF deposit and post-spray aging to land you back at drawing with full mechanicals.

Technical data

Hardness
280-380 HV as-sprayed HVOF typical; published HVOF work reports ~560 HV0.2 dense deposits and up to ~695 HV0.1 after post-spray aging (precipitation of γ′ + γ″). Treat as two numbers: as-sprayed and aged
Bond strength
8,500-10,500 psi HVOF (58-72 MPa); peer-reviewed aeronautic-repair work documents >43-58 MPa on grit-blasted steel/superalloy substrates
Max service temp
~1200-1300°F continuous for coating duty (wrought parent alloy rated to 1300°F / 704°C per Special Metals/HTM); strength falls off sharply above 650°C as γ″ overages
Max service temp
~650-704°C continuous; useful strength retained cryogenic-to-650°C, which is the alloy's defining envelope
As-sprayed porosity
<1.5% HVOF (typ. 0.5-1.5%); HVAF and optimized HVOF parameters push below 1%, oxide content <1% on liquid-fuel guns
Typical thickness
10-60 mils HVOF (250-1500 µm) for build-up and dimensional restoration; Oerlikon Metco DSMTS-0085 cites HVOF thickness limits of 1.5-2.5 mm (60-100 mils) depending on geometry — Inconel 718 is a cladding/build-up alloy, not a thin flash
Density
8.19

Where it earns its keep

  • Age-hardenable after spray: post-spray precipitation treatment (solution anneal + 1325°F / 1150°F double age per AMS 5663) drives microhardness from ~560 HV0.2 as-sprayed to ~695 HV0.1, delivering true superalloy mechanical properties in the deposit
  • Wrought-spec composition (AMS 5662/5663, UNS N07718) supports aerospace qualification pathways and like-on-like repair of parent Inconel 718 parts
  • Retains useful strength cryogenic-to-650°C — fills the gap between corrosion-only 625 overlays and hot-section MCrAlY coatings
  • Supports thick HVOF build-up (up to 60-100 mils per Metco DSMTS-0085) for dimensional restoration of worn engine hardware
  • API 6ACRA / NACE MR0175 pathway available for sour-service oil & gas with controlled chemistry and aging — safety valves, packers, tubing hangers rated to 20,000 psi
  • Weldable and compatible with standard Inconel 718 repair heat-treat cycles already on file at aerospace MROs

Where it doesn't

  • Precipitation-hardening mechanism requires controlled post-spray solution + double-age heat treat to hit full strength — shops without aerospace-grade vacuum furnace and recipe control will get as-sprayed properties only
  • Not a wear coating in its own right: at 280-380 HV as-sprayed it loses a gouging fight with WC-Co (1200+ HV) or Stellite 6 (500+ HV). Use it for build-up, restore-to-drawing, and corrosion — not abrasion
  • Best deployed as cladding / build-up (10-60 mils and above), not thin protective flash — through-porosity risk in aggressive service at <10 mils
  • Higher raw-powder cost than plain nickel or stainless alloys (Cr + Nb + Mo + Ti loading); economics favor higher-value aerospace and oilfield parts, not general industrial wear
  • Service ceiling is ~650°C — above that γ″ overages and the strength advantage collapses; use MCrAlY + TBC stacks for true hot-section duty
  • Chloride-SCC performance is good but not the 625-grade immunity; specify carefully for seawater duty

Typical applications

  • Aerospace gas-turbine compressor blade tip repair and dimensional restoration
  • Compressor vane, stator, and casing refurbishment on hot- and cold-section engine hardware
  • Shaft seal teeth / labyrinth seal land build-up on turbine rotors
  • Cold-section superalloy part build-up where wrought-spec composition supports aerospace qualification
  • Turbine disc and spacer refurbishment (critical rotating parts)
  • Oil & gas subsurface safety valves, packers, tubing hangers, flow-control bodies in 15,000-20,000 psi sour service
  • Downhole wellhead trim and sour-service fastener overlay
  • Rocket engine and space-propulsion hardware refurbishment (heritage NASA M-1 engine pedigree)
  • Industrial gas-turbine hot-section dimensional restoration below 650°C
  • High-strength corrosion-resistant overlay on steel valve bodies and shafts for chemical/petrochemical service

Wear modes addressed

  • Dimensional loss from erosion, fretting, and blade-tip rub (primary repair driver)
  • Galling and adhesive wear on seal lands and mating surfaces
  • Sour-service corrosion (H2S/CO2/chlorides) in oil & gas components
  • High-temperature oxidation to 650°C on engine hardware
  • Stress-corrosion and crevice attack in downhole brines
  • Thermal-mechanical fatigue on turbine hot-section parts

Industries

  • Aerospace (jet engine OEM and MRO)
  • Space propulsion and launch vehicle hardware
  • Industrial gas turbines (power generation, mechanical drive)
  • Oil & gas (downhole, wellhead, subsea, sour service)
  • Chemical and petrochemical process
  • Cryogenic process equipment
  • Defense and military turbine MRO

Substrates

  • Inconel 718 parent parts (like-on-like aerospace repair)
  • Other Ni-base superalloys (Inconel 625, 706, Waspaloy, Rene alloys — with dilution control)
  • 17-4 PH and PH13-8Mo stainless steels
  • AISI 4140 / 4340 shafts and casings for build-up
  • Low-alloy and stainless steel valve and wellhead bodies
  • Cast iron and gray iron (industrial retrofit — published HVOF work on GCI demonstrates strong adhesion)

Which process, when?

HVOF is the mainstream thermal-spray route for Inconel 718 repair: dense (<1.5% porosity), strong bond (>58 MPa), fine lamellar microstructure, and supports 10-60 mil build-up for compressor blade tips, seal teeth, and valve bodies. HVAF (high-velocity air-fuel) runs cooler than HVOF and produces even lower oxide content and porosity (<1%) on the same alloy — emerging as the preferred process for aerospace repair where oxide stringers in the deposit are the limiting factor. Atmospheric plasma spray (APS) is a long-qualified aerospace process for Inconel 718 but gives higher porosity (2-5%) and more oxide; still used where part geometry blocks HVOF line-of-sight. Cold spray is a strong contender for thick 718 build-up with near-zero porosity and no thermal distortion, and pairs well with a downstream solution + age cycle to develop full strength. Pick HVOF for the default dimensional-restoration job; pick HVAF or cold spray when oxide or heat input is the blocker; pick DED when the drawing calls for wrought-equivalent mechanicals through the full section.

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.

Thinking about Inconel 718 for a part?

Send us the spec or a photo. We'll tell you whether this fits, or point you at a better material for the job.

Ask about this material