PS 400
Ni, Mo, Al, CrO₂, Ag + fluorides
- Plasma
PS 400 is NASA Glenn's current-generation self-lubricating composite coating — the latest of the PS-series (PS100 → PS304 → PS400), developed by Christopher DellaCorte and Brian Edmonds for oil-free turbomachinery. It's a plasma-sprayed composite: a NiMoAl binder (90 Ni / 5 Mo / 5 Al) at roughly 70 wt%, Cr₂O₃ as the hardening phase, silver as the low-temperature lubricant, and a BaF₂/CaF₂ eutectic as the high-temperature lubricant. That single matrix covers the tribological envelope from room temperature through ~650°C continuously, with useful performance out to 900°C.
The design goal was to fix what held PS304 back. Swapping the NiCr binder for NiMoAl delivered better creep resistance and dimensional stability — no thickness swelling after 760°C soaks — and the molybdenum addition improved as-sprayed density. Surface finish came down to ~0.25 µm rms (vs. ~0.8 µm), and the coating no longer needs a post-spray heat treatment. Solid-lubricant loading was halved without losing performance.
Primary application: oil-free gas-turbine foil bearings and emerging APU / microturbine hot-section hardware. NASA licenses through ADMA Products and Hohman Plating; not a catalog powder. PS 400 earned NASA's 2018 Invention of the Year and has logged 20,000+ turbine engine test hours. For aerospace tribology and oil-free rotating machinery, this is the NASA-backed answer — specialty sourcing, specialty spray window, worth the conversation.
Technical data
- Max service temp
- 1,200°F continuous demonstrated (650°C pin-on-disk + foil-bearing testing); useful tribological performance reported to ~1,650°F (900°C); total environmental envelope ~-238°F to >1,650°F (-150°C to >900°C) per NASA commercialization summary
- Max service temp
- 650°C continuous demonstrated; useful to ~700-900°C; cryo-capable to ~-150°C
- As-sprayed porosity
- Dense plasma-sprayed deposit — measurably higher density than PS304; PM400 (powder-metallurgy solid) is fully dense
- Typical thickness
- 10-30 mils (0.25-0.75 mm) plasma-sprayed onto bearing races, foil-bearing journals, and sleeve surfaces; ground-and-polished finish after spray
Where it earns its keep
- Self-lubricating from room temperature through 650°C with useful performance to ~900°C — a single coating covers the whole operating band
- Enables oil-free turbomachinery: eliminates lube-oil systems, pumps, filters, and scavenge hardware in APUs, microturbines, and next-generation turbine engines
- Higher as-sprayed density and smoother finish than PS304 (0.25 µm rms vs. ~0.8 µm rms) — lower break-in wear on counterface foils
- No post-deposition heat treatment required, unlike PS304 — direct reduction in processing cost and lead time
- NiMoAl binder (vs. PS304's NiCr) delivers improved creep resistance and dimensional stability — no thickness swelling after 760°C soaks
- Halved solid-lubricant loading (5% Ag + 5% fluoride vs. PS304's 10%+10%) with equivalent tribological performance — more binder, stronger coating
- NASA's 2018 Government and Commercial Invention of the Year; >20,000 cumulative turbine engine test hours documented
Where it doesn't
- Specialty coating — not a commodity thermal-spray product; deposition is licensed through NASA Glenn (ADMA Products, Hohman Plating) or performed under technology-transfer agreement
- Requires tightly controlled plasma-spray parameters: particle size (Cr₂O₃ 40-120 µm), spray distance, and feed rates must stay in the NASA-developed window
- Ag content can volatilize at prolonged >700°C service — fluoride eutectic carries lubricity beyond the silver regime but long-duration data above 800°C is still being accumulated
- Counterface selection matters — NiMoAl PS400 on superalloy gives the best-documented wear pair; aggressive hard-ceramic counterfaces can abrade the Ag/fluoride phases too quickly
- Low-volume / high-value market: the cost structure targets aerospace turbomachinery and specialty rotating hardware, not high-throughput industrial wear parts
- Grinding after spray uses SiC wheels per the NASA spec; diamond grinding is not recommended on the Ag/fluoride phase
Typical applications
- Oil-free gas-turbine foil air bearings (primary target application — journal and thrust foil-bearing wear surfaces)
- Aerospace auxiliary power units (APUs) using oil-free compressor and turbine bearing architectures
- Microturbine and turbocharger rotor bearing surfaces for hot-section oil-free operation
- Rocket-engine and turbopump bearing and seal running surfaces where oil lubrication is infeasible
- Shaft sleeves and bushings in high-temperature rotating machinery (industrial and aerospace)
- Thrust washers, lift valves, and other cyclic high-temperature sliding pairs
- Automotive exhaust-system components and exhaust-gas-recirculation (EGR) valves (ADMA / Hohman Plating commercial licensees)
- Unmanned aerial vehicle (UAV) propulsion bearing hardware and other weight-sensitive oil-free rotating systems
Wear modes addressed
- High-temperature adhesive wear at metal-to-metal or metal-to-superalloy contacts (primary design target)
- Sliding wear at startup/shutdown transient contact in foil bearings (before aerodynamic liftoff)
- Oxidation of the NiMoAl binder at prolonged >700°C exposure — markedly slower than PS304's NiCr binder
- Loss of Ag lubricant by volatilization and diffusion at the highest service temperatures (Ag phases out above ~500°C; fluoride eutectic takes over)
- Abrasive wear from ingested debris in dusty or particulate-laden hot-gas service
Industries
- Aerospace (oil-free turbine propulsion, APUs, rocket-engine turbopumps)
- Microturbine and distributed power generation (oil-free hot-section bearings)
- Automotive and heavy-duty diesel (exhaust, EGR, turbocharger hardware — via NASA licensees)
- Space exploration and in-space mechanisms (vacuum-compatible solid lubrication)
- UAV and small-turbine propulsion OEM
- Research-grade bearing and seal development for high-temperature rotating machinery
Substrates
- Nickel-base superalloys (Inconel 625, 718, X-750) — the primary turbine/bearing substrate family
- Cobalt-base superalloys (Haynes 25 / L-605, MAR-M509) in hot-section hardware
- Stainless steels (304, 316, 17-4 PH, A286) for lower-temperature bearing and sleeve work
- Titanium alloys (Ti-6Al-4V) where interfacial bond chemistry is controlled
- Tool and hot-work die steels (H13) for laboratory and development samples
Which process, when?
Plasma spray is the deposition method of record for PS400 — NASA's patented composition was formulated around an atmospheric plasma-spray (APS) deposition window, and commercial licensees ADMA Products and Hohman Plating run PS400 through APS for bearing and turbine hardware. The coating is then ground and polished with silicon-carbide wheels to the target ~0.25 µm rms finish; no post-deposition heat treatment is required, which is a processing-cost win over PS304. PM400 is the free-standing powder-metallurgy form of the same composition — used where a bulk solid is needed (bushings, thrust washers) instead of a coating on a superalloy substrate. HVOF is not the typical PS400 process: the coating was designed around plasma-spray densification of a NiMoAl binder plus Cr₂O₃ hardener plus Ag and BaF₂/CaF₂ eutectic, and HVOF's combustion chemistry can over-oxidize the binder and degrade the fluoride lubricant. Selection is driven by substrate geometry (APS for foil-bearing journals and shaft sleeves) and by licensing availability (PS400 is not a catalog powder you buy off the shelf — it's a controlled NASA technology-transfer product).
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.
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DellaCorte, C. & Edmonds, B.J. — NASA/TM-2009-215678: NASA PS400, A New High Temperature Solid Lubricant Coating for High Temperature Wear Applications (NASA Glenn Research Center, 2009)
“PS400 is comprised of a nickel-molybdenum-aluminum binder that provides strength, creep resistance and extreme oxidative and dimensional stability. Chromium oxide, silver and barium-calcium fluoride eutectic are added to the binder to form PS400. Tribological properties were evaluated with a pin-on-disk test rig in sliding contact to 650°C; PS400 exhibits tribological characteristics comparable to PS304 but with enhanced creep resistance and dimensional stability. Surface rms finishes of about 0.25 µm are typical for PS400 — three to four times smoother than PS304.”
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US Patent 8,753,417 B1 — High Temperature Solid Lubricant Coating for High Temperature Wear Applications (Inventors: Christopher DellaCorte, Brian J. Edmonds; Assignee: NASA, 2014)
“Metal binder comprises about 50-90 weight percent of the composite (preferred 70 wt%) with nominal 90 Ni / 5 Mo / 5 Al; chromium oxide hardener 5-35 wt% (preferred ~20 wt%); metal fluoride lubricant 1-20 wt% (preferred ~5 wt% BaF₂/CaF₂ eutectic); low-temperature lubricating metal 0.1-20 wt% (preferred ~5 wt% Ag). Plasma-spray deposition followed by SiC grinding. No post-deposition heat treatment required.”
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Radil, K. & DellaCorte, C. — The Performance of PS400 Subjected to Sliding Contact at Temperatures from 260°C to 927°C (US Army Research Laboratory / NASA Glenn; DTIC AD1032092)
“PS400 coating hardness approximately HRA 59. The coating demonstrates effective tribological performance under sliding contact through the 260-927°C range, confirming its suitability for hot-section bearing and seal applications in oil-free turbomachinery.”
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NASA Tech Briefs LEW-18561-1P — NASA PS400 High-Temperature Solid Lubricant Coating (NASA Glenn Technology Transfer)
“PS400 combines a nickel-molybdenum-aluminum binder, chromium-oxide hardener, silver lubricant, and barium fluoride/calcium fluoride eutectic lubricant. The coating functions across a wide temperature range in air, vacuum, and hydrogen-rich reducing environments, produces smooth surfaces with excellent dimensional stability, and requires no post-deposition heat treatment prior to service.”
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Aerospace Manufacturing & Design — Solid Lubricant Coating is NASA's Invention of the Year (2018 Government and Commercial Invention of the Year Award)
“PS/PM400 operates across an extreme temperature range of approximately -150°C to greater than 900°C. Developed by Dr. Christopher DellaCorte and Brian J. Edmonds at NASA Glenn Research Center. NASA licensed the technology to ADMA Products and Hohman Plating for commercial development in rocket engines, aircraft turbines, foil air bearings, automotive exhaust and EGR valves, and UAV propulsion components.”
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Tribological Behavior of PS400-Related Tribopairs for Space Exploration — Tribology International (peer-reviewed)
“NiMoAl-Cr₂O₃-Ag-BaF₂/CaF₂ (PS400) coatings provide low wear and friction throughout 25-700°C, with the NiMoAl matrix replacing PS304's NiCr to fix dimensional-stability and creep-resistance issues while halving total solid-lubricant loading.”
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NASA Technology Transfer Portal LEW-TOPS-121 — Oil-Free Lubricants (PS/PM400 family commercialization)
“PS/PM400 enables efficiency increases of up to 40% in rotating machinery applications and has proven durable in over 20,000 hours of turbine engine operation. Target applications include oil-free turbochargers, auxiliary power units, and turbine propulsion systems for aircraft.”
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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