Structural Ceramics

Structural Ceramics

Technology is putting increasing demand on materials where applications require greater strength, hardness, wear resistance, corrosion resistance, high temperature stability and reduced weight.

Due to their high melting point and good mechanical properties compared to metal and polymers, ceramics are finding increased application.

A major limitation for ceramics is poor fracture toughness, therefore major focus for the ceramic industry has been the development of ceramic composites.

In the world of ceramic materials, yttria doped zirconia, in particular yttria stabilised tetragonal zirconia polycrystalline Y-TZP ceramic is a strong candidate for structural applications due to excellent strength (700-1200 MPa) and fracture toughness (2-10 MPa m1/2) in addition to good chemical inertness.

The high toughness of zirconia monoliths stems from the stress induced transformation of the tetragonal phase to the monoclinic phase in the stress field of propagating cracks – 'Transformation toughening'. The micro structure requirements are for maximum retention of the tetragonal phase at the application temperature with sufficient transformability to monoclinic in the crack tip stress field.

Zirconia finds application in marine pump seals and shaft guides, precision ball valves and seals, milling media, thread and wire guides, deep well valves and seals.

Typical Engineering Performance Data for Yttria Zirconia

PropertyValueUnits
     
3 point RT Modulus of Rupture (Specimen 3 × 3 × 50mm, span 19.05mm) 1000 MPa
Weibull Modulus 15 -
RT Unit Tensile Strength 500 MPa
RT Compressive Strength >2000 MPa
RT Young's Modulus of Elasticity 205 GPa
RT Hardness (HRA) 91 -
RT Hardness (Vickers Hv0.3) 1350 Kg/mm2
Fracture Toughness K¹C 8.0 MPam½
Density 6.04 g/cc
Porosity 0 %
Thermal Expansion Coefficient (0-1200°C) 10.0X10-6 K-1
RT Thermal Conductivity 2.0 W/(mK)
Thermal Shock Resistance 250 ΔT°C
Maximum Use Temperature 1000 °C
RT Electrical Resistivity 109 ohm m
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