HTS Coatings — machining & grinding

300 Series Stainless Steel

10–14% Ni, 2% Mo, 1% Mn, 16–18% Cr, Fe-balance

  • Flame
  • Arc
  • Plasma
  • HVOF

300 Series Stainless Steel — AISI 316L chemistry in coating form — is the corrosion workhorse of our stainless lineup. Roughly 17% chromium, 12% nickel, 2% molybdenum, balance iron. The molybdenum is the headline: it upgrades pitting and crevice resistance in chloride service well beyond plain 304, which is why 316L is the default stainless for marine, food, pharma, and mild-chemical duty. On the hardness chart it's soft — 200-300 HV as-sprayed, sometimes pushed to 345+ HV with tuned HVOF parameters — so we don't reach for this coating when abrasion is the enemy. We reach for it when corrosion is.

At HTS we apply 300-series stainless across all four processes. Arc-spray (TWAS) is the workhorse for large-area build-up on carbon-steel tanks, marine topside hardware, and structural steel — fast, 20-40 mils in a shift, porosity sealed for aggressive service. HVOF is the premium option for wet-pump components and valve trim where a dense, machinable, <2% porosity deposit holds corrosion without a sealer. Plasma tightens the microstructure for pump internals; flame-spray handles field repair. Cross-references include Metco 41C, 42C, 43C-NS, AMPERIT 316L and 321.

Got a carbon-steel tank eating itself, a worn 316L pump shaft, or marine hardware needing build-up? Send us the part — we'll scope the right process, thickness, and sealer.

Technical data

Hardness
200-300 HV typical as-sprayed — austenitic and intentionally soft; flame-spray deposits run ~190 HV, APS ~260 HV, arc-spray ~325 HV, HVOF 270-345 HV, HVAF up to 345 HV. Published research pushes HVOF to 400+ HV with tuned parameters, but this is a corrosion/build-up coating, not a wear coating
Bond strength
Arc-spray 3,000-6,000 psi (21-41 MPa) typical on grit-blasted carbon steel; HVOF 7,000-9,000 psi (48-62 MPa); cold-spray 4,000-4,500 psi (~29 MPa) per J. Thermal Spray Technology; published TWAS data reports up to 50 MPa with tuned parameters
Max service temp
~1000°F (540°C) continuous per Oerlikon Metco DSMTS-0078 guidance for austenitic stainless coatings; useful short excursions somewhat higher for oxidation stability only
Max service temp
~540°C continuous; austenitic 316L parent is rated higher in wrought form, but as-sprayed deposits with residual oxide and porosity de-rate the practical ceiling
As-sprayed porosity
Arc-spray 5-12% (high — sealing recommended for aggressive service); flame-spray 5-10%; APS 2-5%; HVOF <2% (typ. 0.5-2%); HVAF <1%. Porosity and hardness track inversely — denser deposits measure harder
Typical thickness
Arc-spray 20-40 mils (500-1000 µm) — thick because porosity demands it for corrosion service; HVOF 6-20 mils (150-500 µm) sufficient in sealed service; HVAF effective at ~4 mils (100 µm) per Kermetico; build-up for dimensional restoration up to 60 mils (1.5 mm)
Density
7.95-8.00 (austenitic Fe-Cr-Ni-Mo)

Where it earns its keep

  • Austenitic corrosion resistance — chromium + nickel + molybdenum handles mild chloride, pitting, and crevice service where carbon steel fails
  • Non-magnetic deposit — valuable for medical, sensor, and pharma service where stray magnetism is a concern
  • Widely available and inexpensive relative to nickel superalloys (Inconel 625, Hastelloy C-276) — 316L wire and powder are commodity feedstocks
  • Arc-spray is fast and cost-effective for large areas — tank interiors, structural columns, and ship topsides coat in hours, not days
  • Machinable with ordinary steel tools to a good finish — supports dimensional restoration workflows
  • Compatible with all four thermal-spray processes (flame, arc, plasma, HVOF) — shop can match process to duty and budget

Where it doesn't

  • Soft (200-300 HV) — this is a corrosion and build-up coating, not a wear coating. Pick Stellite, WC-Co, or Cr3C2-NiCr for abrasion or sliding wear
  • Arc-spray porosity is high (5-12%) — sealing with epoxy, silicone, or aluminum phosphate is mandatory for aggressive aqueous or chloride service
  • Max continuous service temperature ~540°C in coating form — well below the wrought 316L ceiling due to oxide stringers and lamellar porosity paths
  • Molybdenum content helps pitting in chloride service but the coating is not a chloride-immune option — for seawater immersion, specify Inconel 625 or Hastelloy C-276
  • Where the design allows it, wrought 316L plate or weld overlay will outperform a sprayed deposit on through-thickness corrosion resistance — thermal spray's niche is refurbishment, build-up, and geometry that can't be welded or re-forged

Typical applications

  • Corrosion-resistant build-up on carbon and low-alloy steel substrates (tanks, vessels, structural members)
  • Wet-pump wear rings, impellers, and casings in process water and mild chemical service
  • Marine hardware build-up — deck fittings, handrail stanchions, topside brackets where galvanizing is insufficient
  • Food and pharmaceutical component refurbishment — mixer shafts, conveyor parts, washdown hardware
  • Decorative corrosion coating on structural steel — architectural columns, railings, exposed fasteners
  • Dimensional restoration of worn 316L and 304 substrates before re-machining
  • Anti-galling surface on mated stainless-on-stainless fasteners and valve trim (paired with Mo wire in arc spray)
  • Paper-mill stock-line and white-water piping protection
  • Mild chemical-process piping and heat-exchanger shell exteriors
  • Tank and vessel interior liners for water treatment and condensate service

Wear modes addressed

  • General aqueous corrosion (clean water, mild chemical, condensate)
  • Pitting and crevice corrosion in low-chloride service (molybdenum addition is the defense)
  • Mild erosion-corrosion in wet pump flow paths
  • Atmospheric weathering on marine topside and structural steel
  • Galling and adhesive wear on stainless-on-stainless fastener threads (anti-galling use)
  • Cavitation in low-intensity pump service (sealed HVOF deposits only)

Industries

  • Water and wastewater treatment
  • Pulp and paper (stock line, white water, mild chemistry)
  • Marine and offshore (topside, non-immersion hardware)
  • Food processing and dairy
  • Pharmaceutical and biotech (washdown, non-product-contact)
  • Architectural and structural steel (decorative corrosion)
  • General chemical process (mild service)
  • Pump and valve manufacturing (repair / build-up)

Substrates

  • Carbon steel (A36, 1018, 1045) — the primary use case for build-up and corrosion cover
  • Low-alloy steels (4140, 4340) for shaft and pump-component refurbishment
  • Cast iron pump housings and valve bodies
  • Stainless substrates (304, 316, 316L) for dimensional restoration
  • Ductile iron for marine and water-service hardware
  • Galvanized steel (surface-prepped) for heavier marine build-up

Which process, when?

Arc-spray (TWAS) is the workhorse for 300-series stainless — fast, cheap, portable, and ideal for large-area build-up on tanks, structural steel, and marine hardware. Porosity runs 5-12% and deposits need sealing for aggressive service, but the cost-per-square-foot is unbeatable and a skilled technician lays down 20-40 mils in a single shift. Flame spray (wire or powder) is the fallback for field repair where arc-spray equipment isn't available; expect similar porosity and slightly softer deposits. Plasma spray (APS) tightens porosity to 2-5% and gives a more uniform microstructure, useful for pump internals and valve trim where a machined finish matters. HVOF is the premium option — dense (<2% porosity), strong bond (48-62 MPa), machinable to fine finishes, and the right answer when the coating has to carry corrosion load without a separate sealer. HVAF edges HVOF on oxide content and achieves gas-tight protection at just 4 mils. Pick arc for area coverage, HVOF for sealed service, plasma for geometry, flame for field work.

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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