# Zirconia alumina abrasive

Fused alumina-zirconia grain families, producer-specific chemistry and microstructure, treatments, hardness and packing measurements, sizing systems, and performance limits.

Reviewed: 2026-10-29

Tags: abrasives, alumina, zirconia, grains

## Identity and terminology

Saint-Gobain’s AZ40 **1575** treatment is for electrostatic coating and **1578** is for resin bonding in thin wheels. Both list a typical **39.0% ZrO₂**. [AZ product page](https://www.abrasivematerials.saint-gobain.com/products/alumina-zirconia-abrasive-grains/az25az40-alumina-zirconia-grains) [Thin-wheel grain applications](https://www.abrasivematerials.saint-gobain.com/applications/bonded-abrasives/bonded-abrasive-grains-thin-wheels) Alumina-zirconia chemistry, shape and treatment vary by grain. [FEPA abrasive grains](https://www.fepa-abrasives.com/abrasive-products/grains/)

The AZ25 1520 sheet describes primary corundum with an alumina-zirconia eutectic. The bonded AZ40 sheet describes a columnar eutectic. [AZ25 1520](https://www.abrasivematerials.saint-gobain.com/files/311/download) [AZ40 1564 and 1578](https://www.abrasivematerials.saint-gobain.com/files/316/download)

Zirconia-toughened alumina, ZTA, also names structural ceramic materials. Ceramco's ZTA8, for example, is an 85% alumina and 15% zirconia formulation for formed OEM components. That component material is a separate reference from fused abrasive grain. **Synthesis.** Structural-ceramic strength and toughness tables cannot supply properties for an abrasive identified only as "zirconia alumina." [Ceramco ZTA8](https://www.ceramcoceramics.com/materials/zta/zta.php)

## Named chemistry and grain variants

The following are typical producer values, not universal specifications or analyses of a supplied lot. The chemical tables print percentages. They do not identify a chemical-analysis method or fully define the percentage basis. The bonded AZ40 description separately uses approximately 40 wt% zirconia. Its chemical table reports 39.0%, illustrating the distinction between a family label and a reported analysis.

| Saint-Gobain grain codes | Al₂O₃, % | ZrO₂, % | TiO₂, % | Y₂O₃, % | Named form or treatment |
| --- | --- | --- | --- | --- | --- |
| AZ25 1520 | 74.5 | 25.0 | 0.08 | Not listed | Strong grain, untreated |
| AZ40 1564 and 1578 | 60.0 | 39.0 | 0.15 | 0.65 | Strong grain, untreated 1564 or treated 1578 |
| AZ40 1565 and 1575 | 60.0 | 39.0 | 0.15 | 0.65 | Weak grain, untreated 1565 or treated 1575 |
| ZF 1525 and ZS 1526 | 75.0 | 23.0 | 0.10 | Not listed | Untreated, strong ZF or ultra-strong ZS |

The rows come from the [AZ25 bonded sheet](https://www.abrasivematerials.saint-gobain.com/files/311/download), [AZ40 bonded sheet](https://www.abrasivematerials.saint-gobain.com/files/316/download), [AZ40 coated sheet](https://www.abrasivematerials.saint-gobain.com/files/321/download), and [ZF and ZS sheet](https://www.abrasivematerials.saint-gobain.com/files/296/download). Other constituents appear in those sheets. The selected columns are not complete formulations. An unlisted constituent is not a certified zero.

The ZF and ZS sheet distinguishes crushed, blocky ZF with sharp edges from ZS with rounded, mulled edges. It associates ZF with resin-bonded foundry wheels and ZS principally with resin-bonded steel-conditioning wheels. These are producer application descriptions rather than interchangeability claims. [ZF and ZS, page 1](https://www.abrasivematerials.saint-gobain.com/files/296/download)

Saint-Gobain's live AZ page identifies 1575 treatment with electrostatic coating. Its thin-wheel page identifies 1578 treatment with resin bonding. Treatment purpose therefore depends on the code, even within AZ40. [AZ25 and AZ40 product page](https://www.abrasivematerials.saint-gobain.com/products/alumina-zirconia-abrasive-grains/az25az40-alumina-zirconia-grains), [Thin-wheel grain applications](https://www.abrasivematerials.saint-gobain.com/applications/bonded-abrasives/bonded-abrasive-grains-thin-wheels)

## Crystal size, hardness, and density

| Typical property, as labeled by the producer | AZ25 1520 | AZ40 bonded 1564 and 1578 | AZ40 coated 1565 and 1575 |
| --- | --- | --- | --- |
| Crystal size | 17 µm | 12 µm | 12 µm |
| Vickers hardness, 50 gram load | 21 GPa | 19 GPa | 19 GPa |
| "Specific gravity," printed with g/cm³ | 4.30 | 4.60 | 4.60 |
| Loose packed density, g/cm³ | 2.00 to 2.40 | 1.97 to 2.35 | 1.715 to 2.220 |

Sources are the three [AZ25](https://www.abrasivematerials.saint-gobain.com/files/311/download), [bonded AZ40](https://www.abrasivematerials.saint-gobain.com/files/316/download), and [coated AZ40](https://www.abrasivematerials.saint-gobain.com/files/321/download) sheets, page 1. They give no full indentation, density, or crystal-size measurement procedure. Specific gravity is conventionally dimensionless. The table retains the sheets' label and unit rather than silently treating the entries as a defined density test.

**Synthesis.** Crystal size describes internal structure, not whole-particle grit size. Loose packed density includes space between particles and depends on packing. It cannot replace particle density in a solid-volume calculation. Vickers indentation hardness, Mohs scratch hardness, and grain-fracture resistance describe different behavior. A hardness number supplies neither a fracture-toughness value in MPa√m nor a fracture index under a named crushing or milling test. These sheets establish no such index.

## Phase behavior and the limits of self-sharpening evidence

Erlacher and colleagues studied Imerys ZK40, a commercial Ti-stabilized fused-cast grain. Table 1 reports XRF oxide concentrations of 55.32 wt% Al₂O₃, 40.44 wt% combined ZrO₂ + HfO₂, 3.57 wt% TiO₂, and 0.07 wt% Y₂O₃. The combined zirconium-and-hafnium entry is not a separate measurement of pure ZrO₂. [2025 original study, methods and table 1](https://doi.org/10.1016/j.oceram.2025.100798)

The study used dry-air annealing at 400, 800, and 1200 °C, with one-hour holds and 3 °C/min heating and cooling. SEM showed cracks along eutectic-domain boundaries after 800 °C annealing. Powder X-ray diffraction with Rietveld analysis identified monoclinic, tetragonal, and cubic zirconia. The authors interpreted transformation-associated cracking and domain loss as a self-sharpening mechanism. This was a thermal and microstructural investigation, not a grinding-life comparison. [Study, sections 2 to 4](https://doi.org/10.1016/j.oceram.2025.100798)

The paper notes uncertainty in amorphous-phase quantification because silicon-standard and monoclinic-zirconia peaks overlap. Its abstract reports up to 13.4% volume expansion, while its conclusion states 14.4%. That discrepancy remains unresolved. [Study, sections 3.4.1 and 5](https://doi.org/10.1016/j.oceram.2025.100798)

**Synthesis.** ZK40's Ti-rich chemistry does not establish AZ40's stabilizer behavior. Neither a typical oxide list nor the word zirconia establishes phase fractions, transformation toughening, or a shared fracture mechanism. The study's annealing temperatures are not recommended grinding temperatures or service limits. A proposed self-sharpening mechanism does not prove freedom from dulling, loading, or grain loss.

## Size designation and distribution

FEPA's public catalog separates F-series bonded-abrasive grains from P-series coated-abrasive grains. It also lists standards specifically for other abrasive materials. Those public titles establish scope distinctions, not a distribution table or automatic conformity for every alumina-zirconia grade. [FEPA grains catalog](https://fepa-abrasives.org/categorie-produit/grains/)

The producer's actual designation remains material-specific. AZ25 lists F4 to F36 with modified ANSI sizing, while its detailed table uses T labels. Bonded AZ40 lists F8 to F220 with modified ANSI sizing. Coated AZ40 lists P20 to P220 with modified FEPA P sizing, including T and SP labels in its detailed distribution table. An F or P prefix in a product table therefore does not erase an explicit "modified" qualification. [AZ25, pages 1 to 2](https://www.abrasivematerials.saint-gobain.com/files/311/download), [Bonded AZ40, pages 1 to 2](https://www.abrasivematerials.saint-gobain.com/files/316/download), [Coated AZ40, pages 1 to 2](https://www.abrasivematerials.saint-gobain.com/files/321/download)

**Synthesis.** These sources establish no universal equivalence among FEPA, ANSI, and JIS designations. A grit number is not one particle diameter or a surface-roughness result. The exact grading system, producer modifications, and distribution basis remain part of a grain's identity.

## Application and performance limits

Saint-Gobain associates coated AZ40 1565 and 1575 with belts, flap discs, and fiber discs. Its claims about wear resistance, cutting efficiency, and life concern named products. They are not comparative test results for every zirconia-alumina tool. [AZ25 and AZ40 product page](https://www.abrasivematerials.saint-gobain.com/products/alumina-zirconia-abrasive-grains/az25az40-alumina-zirconia-grains)

**Synthesis.** Finished-tool performance also depends on bond or backing, grain concentration and orientation, additives, workpiece, contact conditions, speed, cooling, and dressing. The sources establish no universal mechanical ranking, workpiece compatibility list, operating pressure, rated speed, achievable finish, removal rate, cooling advantage, or reuse life. None establishes a customer's installed product or process capability. Safety information for zirconium metal cannot establish behavior of these oxide grains.

## Source versions and coverage

Reviewed on October 29, 2026 PDT. The AZ25 sheet carries a 2022 copyright. The bonded and coated AZ40 sheets show no edition date in their text. The ZF and ZS sheet carries CGN2016-08-01, SG-SGP-09_E01, and a 2016 copyright. AZ25 and ZF/ZS disclaim guarantee or warranty. Undated live pages and download endpoints are retrieval snapshots, not immutable editions.

The original study is Erlacher et al., *Open Ceramics* 22, 2025, article 100798, available online May 26, 2025. It discloses Imerys Technology Center funding. [Published study](https://doi.org/10.1016/j.oceram.2025.100798)

Coverage is limited to the named producer examples and one original thermal study. It excludes lot certification, universal phase proportions, complete measurement procedures for producer physical values, finished-tool qualification, and paid-standard distribution requirements. No paid standard text is reproduced.

## Related references

[Brown fused alumina](brown-fused-alumina.md), [ceramic alumina abrasive](ceramic-alumina-abrasive.md), and [Finishing process references](../../processes/finishing/index.md) describe related grain and process subjects.