Yttria-Stabilized Zirconia is thermal insulation, not wear protection. If the enemy is heat — not abrasion, not corrosion — this is the coating.

YSZ is 92% zirconium oxide, 8% yttrium oxide, sprayed by plasma torch onto a part that's already been bond-coated with a metallic MCrAlY layer. That bond coat is not optional. YSZ does not bond directly to nickel superalloy, stainless, cast iron, or anything else. The MCrAlY (NiCrAlY or NiCoCrAlY, typical 4-8 mils) carries the oxidation resistance and the thermal-expansion match; the YSZ sits on top and does the insulating.

The numbers that matter: thermal conductivity around 1 W/m·K (about 1/11th of the superalloy beneath it), engineered porosity of 8-15% for strain tolerance, typical topcoat thickness 8-40 mils. Under turbine duty, that drops metal-substrate temperature 150-300°C. That's how jet engines run flame temperatures past 1,600°C without melting the blades.

Applied on: turbine blades and vanes, combustor liners, rocket nozzle throats, diesel piston crowns, industrial furnace parts. Forty-plus years of NASA, GE, Pratt, and Rolls-Royce service history.

Watch for: spallation at the bond-coat interface, CMAS attack above 1,200°C. Send us the part and the duty cycle — we'll spec the bond coat and topcoat together.

Technical data

Hardness: Not a wear coating — reported Rockwell C 40-45 (~410-450 HV) for APS 8YSZ, but specification is by porosity and thickness, not hardness
Bond strength: 1,500-3,000 psi typical APS (10-21 MPa) against NiCrAlY bond coat; dense/low-porosity grades reach 30+ MPa (4,400 psi)
Max service temp: ~2,400°F coating surface; substrate metal kept below ~2,000°F (ceramic stable to ~2,192°F / 1,200°C before t′ phase breakdown)
Max service temp: ~1,300°C coating surface; 1,200°C phase-stability ceiling for 7-8 wt% Y₂O₃; substrate metal typically held at 1,000-1,050°C
As-sprayed porosity: 8-15% intentional — porosity is what makes YSZ insulate and tolerate strain; dense YSZ is the wrong coating
Typical thickness: 8-40 mils topcoat (200-1,000 µm); diesel piston crowns 4-10 mils; combustion liners and blades 10-20 mils; thick industrial sections to 40+ mils
Density: ~5.6-5.9 as-sprayed (theoretical ZrO₂ ~6.1; porosity accounts for the gap)

Where it earns its keep

Lowest thermal conductivity in the thermal-spray world — 1.0-1.1 W/m·K, about 1/11th of the superalloy it sits on, which drops metal-substrate temperature 150-300°C (270-540°F) under normal turbine duty
Lets engine designers push turbine inlet temperatures higher without melting the blades — more thrust, better fuel burn, longer component life; the reason modern jet engines hit 1,600°C+ at the flame
Engineered 8-15% porosity is a feature, not a defect — those micro-voids are the strain-tolerance mechanism that keeps the ceramic from cracking off the metal as the part cycles thousand of times from cold-start to takeoff
Four-plus decades of in-service aerospace track record starting with Curt Liebert and Stephan Stecura's NASA Lewis (now Glenn) work in the 1970s; 7-8 wt% yttria is the industry-standard composition for a reason
Applied by atmospheric plasma spray (APS) on-site in the coating cell — no vacuum chamber, no exotic infrastructure; suitable for combustor liners, vanes, piston crowns, and repair work alike

Where it doesn't

YSZ is thermal insulation, not wear protection — do not specify it where the duty is abrasion, sliding wear, or hard contact. For that, you want WC-Co, Stellite, or Cr₃C₂-NiCr
The MCrAlY bond coat is not optional. Every YSZ topcoat sits on a metallic bond coat that provides oxidation resistance, CTE matching, and the thermally-grown alumina scale that the ceramic actually adheres to. Spec both layers together or don't spec either
Spallation is the failure mode — when a YSZ coating fails, it comes off in flakes, not in worn-down material. Inspect for edge lift and segmentation cracks; one spalled section on a turbine blade is a return-to-service issue
CMAS attack is the modern durability ceiling — above ~1,200°C, ingested dust and volcanic ash melt into glass, wick into the pore network, and destroy the strain tolerance. Operators flying the Middle East and Pacific Rim routes deal with this constantly; it's an OEM-spec conversation

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.

Cincinnati Thermal Spray — Yttria Stabilized Zirconia (CT1700-1)
“92% ZrO₂ / 8% Y₂O₃; Rc 40-45; bond strength 1,900-2,100 psi; porosity 5-15%; thermal conductivity 1.0-1.1 W/m·K; applied over a hot-corrosion-resistant MCrAlY bond layer for blades, vanes, combustion liners, transition pieces, rockets.”
Oerlikon Metco — Understanding Thermal Barrier Coatings
“YSZ ceramic over an oxidation-resistant metallic MCrAlY bond coat; reduces heat transfer into base material; turbine inlet temperatures have risen ~500°C over four decades while material limits only ~220°C, pushing components past 1,500°C (2,732°F); applied on transition ducts, combustors, heat shields, augmenters, nozzle guide vanes, blades.”
MDPI Coatings — Revisiting the Birth of 7YSZ Thermal Barrier Coatings: Stephan Stecura
“7-8 wt% Y₂O₃-ZrO₂ is the industry-standard TBC composition, established through concurrent plasma-sprayed TBC studies at NASA Lewis (now Glenn) Research Center, most notably component and engine tests championed by Curt Liebert as far back as 1972.”
NASA NTRS — Multilayer TBC Architectures Utilizing Rare-Earth Doped YSZ and Pyrochlores
“Current 7 wt% yttria-stabilized zirconia (7YSZ) has a 1,200°C stability limit; rare-earth doped YSZ and Gd₂Zr₂O₇ pyrochlore layered systems can reduce thermal conductivity ~45% versus YSZ after 20 hr at 1,316°C.”
Höganäs AMPERIT 827 — 7YSZ Plasma Spray Powder
“Agglomerated and sintered 7-8 wt% yttria-stabilized zirconia for atmospheric plasma spraying; standard powder for gas turbine TBC topcoats.”
npj Materials Degradation — CMAS Corrosion Attack on Thermally Sprayed TBCs (Review)
“Molten CMAS infiltrates the porous TBC microstructure through capillary action, destabilizes YSZ by thermochemical reaction, solidifies on cooling, stiffens the coating (Young's modulus ~250 GPa CMAS-infiltrated vs ~40 GPa non-infiltrated), and drives premature spallation.”
Safe Fly Aviation — Thermal Barrier Coatings: The Invisible Shield at 1,600°C
“Modern turbines operate at 1,600-1,700°C in the gas stream; YSZ coatings reduce surface temperature by 150-200°C, protecting nickel-base superalloys that lose structural integrity above 1,000-1,050°C; MCrAlY bond coat 100-150 µm with a naturally formed α-Al₂O₃ thermally-grown oxide.”
MDPI Aerospace — Influence of YSZ TBC on Aerothermal Performance of an Annular Combustor
“YSZ ceramic layer offers a thermal reduction of about 100-300°C for the bond coat surface; lowers substrate temperature by 150-300 K; thermal conductivity ~1.04 W/m·K, ~11× lower than the GH3536 alloy substrate.”
Oerlikon Metco DSMTS-0001.8 — 8% Yttria-Stabilized Zirconia HOSP (Metco 204 NS family)
“ZrO₂ balance with 7.0-8.0 wt% Y₂O₃; HOSP process powders combine pre-alloyed fused-and-crushed properties with spray-dried flowability; used as TBC top coat on combustion liners, transition pieces, afterburners, heat shields, and turbine airfoils for thermal protection to ~900°C component metal.”

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.

Yttria-Stabilized Zirconia

Technical data

Where it earns its keep

Where it doesn't

Typical applications

Wear modes addressed

Industries

Substrates

Sources

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