Industrial zirconia and alumina zirconia grades from Blasch for wear parts, metal handling and superalloy melting.
Most ceramics fail by a crack that runs unchecked.
Zirconia is the one that pushes back.
Zirconia ceramic, zirconium oxide (ZrO2) stabilized for industrial use, outperforms alumina where a part sees impact, sliding wear or bending loads, because its fracture toughness is several times higher. Its thermal expansion is close to that of steel, so it works well in metal assemblies, and alumina zirconia grades resist aggressive superalloy and stainless melts better than plain alumina. Alumina remains the better choice where cost per part and high purity matter most, and silicon carbide where heat has to pass through the wall.
Zirconia is zirconium oxide. Pure zirconia changes its crystal structure as it heats and cools, and the volume change cracks a solid part. Industrial zirconia is therefore stabilized with a small addition of another oxide such as yttria, magnesia or calcia, which keeps the structure stable across the operating range.
The search results for zirconia ceramic are full of dental crowns, rings and watch cases. Industrial zirconia is the same oxide, made for a different job: a nozzle, a valve seat or a crucible that has to survive wear, impact or molten metal for a full campaign.
Blasch casts zirconia and zirconia containing grades net shape in its own process, so a nozzle bore, a thread or a flange comes out of the mold rather than off a grinding wheel. How the Blasch process works
When a crack starts in stabilized zirconia, the grains at its tip change structure and expand, and that expansion squeezes the crack shut before it can run.
Impact and sliding wear: transformation toughening gives zirconia a fracture toughness several times that of alumina. A zirconia valve part or nozzle chips less when a hard particle hits it or a seat slides against it.
Smooth surfaces: Blasch zirconia takes a very smooth surface with a low coefficient of friction, useful where solids slide or metal has to flow without picking up deposits.
Joints with steel: the modulus of elasticity and thermal expansion of Blasch zirconia are close to steel. In a metal holder or flange, both parts grow by a similar amount as they heat up, which keeps stress at the joint low.
Aggressive melts: an alumina zirconia composite resists nickel, cobalt and stainless melts better than plain alumina. Blasch uses it for crucibles, tundishes, launders and nozzles in aerospace, medical and industrial alloy production.
Cost: zirconia is the more expensive oxide. Blasch developed its high alumina ProCaster crucibles as a replacement for zirconia crucibles in many alloys, and keeps zirconia for the melts that need it.
Heat transfer: zirconia conducts heat poorly. That makes it a good insulator, but a poor choice for a heater tube or a thermocouple sheath that has to pass heat quickly; there, silicon carbide or silicon nitride fits.
Long exposure at high temperature: stabilized zirconia can slowly lose its stabilized structure in some atmospheres and temperature ranges. For a part that sits hot for months, the grade and stabilizer have to be chosen with the operating profile.
Procaster-Z (087) is a mullite bonded alumina with at least 5% zirconia. Its Blasch data sheet:
| Property | Value |
|---|---|
| ZrO2 | 5% minimum |
| SiO2 | 7% maximum |
| Bulk density | 179 to 184 lb/ft³ (2.87 to 2.95 g/cm³) |
| Porosity | 20 to 23% |
| Modulus of rupture, room temperature | 1,700 psi (11.7 MPa) |
| Service temperature | 1,650 °C (3,000 °F) continuous, 1,760 °C (3,200 °F) intermittent |
Low iron oxide, calcia and alkali content keeps the grade from reacting with nickel and cobalt alloys. The open porosity is deliberate: it lets the part take fast heating in an induction furnace without cracking.
Besides the wear grades, Blasch makes a metallurgical zirconia for specialty stainless steels and superalloys, where the melt would attack a lower grade refractory.
Blasch values: Procaster-Z (087) material data sheet; ProCaster crucibles product sheet; Blasch zirconia material page. Transformation toughening: R. C. Garvie, R. H. Hannink, R. T. Pascoe, Ceramic steel?, Nature 258, 1975. Stabilization and thermal properties: W. D. Kingery, H. K. Bowen, D. R. Uhlmann, Introduction to Ceramics, 2nd ed., Wiley, 1976.
Zirconia and alumina zirconia parts for metal handling and wear.
Down spouts and pour spouts that keep their bore while alloy runs through.
Valve seats, balls and trims where solids slide and impact.
Sheaths that keep the thermocouple dry in molten metal and slag.
Alumina zirconia crucibles for the most corrosive superalloy melts.
Procaster-Z is also used for launders, snouts and tundishes and in the InterLok segmented crucible lining. Zirconia setters and plates appear in Blasch saggers and setter plates. Most of these parts go into molten metal plants.
Yes. Zirconia is zirconium oxide, an oxide ceramic like alumina. Dental zirconia and industrial zirconia are the same oxide in different grades.
Alumina is usually the harder of the two. Zirconia wins on toughness, which is why it resists chipping and impact better.
Wear parts such as nozzles, valve components and seals, and crucibles, tundishes and nozzles for melting specialty steels and superalloys.
It costs more than alumina, conducts heat poorly and must be matched to its temperature profile. Where none of its strengths are needed, alumina is the economical choice.
Tell us what the part sees: temperature, medium, impact. A Blasch engineer recommends the grade and designs the part from your dimensions.
