Y2O3, additions yield an extremely fine grained (less than I
micron) microstructure known as
Y-PSZ or TZP or
tetragonal zirconia polycstal. The individual grains are
toughened zirconias are characterized by high strength and
fracture toughness approaching that of the cemented carbides. The
characteristics result from stress induced phase transformations
of the tetragonal crystals to the monoclinic phase with a
corresponding change in volume and local stress field. The TZPís
show superior strength and toughness; however, their properties
suffer at high temperatures, thus limiting their use to
applications below 500. The Mg-PSZís retain their desirable
properties at temperatures approaching 1100.
ZrO2 is available in a wide variety of shapes and sizes and
amenable to a wide variety of cold and hot forming techniques.
Zirconia is stable
in oxidizing and mildly reducing atmospheres. It reacts with
carbon, nitrogen and hydrogen at temperatures above 2200. It is
inert to acids and bases at room temperature with the exception of
HF and does not react with the refectory metals up to 1400.
However, the capability is strongly dependent upon the type and
quantity of stabilizer used in the ceramic.
markets for Mg-PSZ, Y-PSZ or TZP include thermal barriers for high
efficiency heat engines, cutting tools, wear parts, biological
implants, certain ferrous metallurgical applications and high
temperature oxygen sensors.
Advanced ZrO2 Ceramics for Structural Applications:
two basic grades of Mg-PSZ and one grade of Y-TZP.
MS GRADE: Superior
fracture toughness and high mechanical strength.average thermal
shock resistance. Best suited applications bellow 800 and minimum
TS GRADE: Excellent
thermal shock resistance, slightly lower strength than MS grade,
but higher toughness. Best suited for high temperature (above 600) applications or thermal cycling.
Superior mechanical Strength and high toughness, slightly lower
thermal shock resistance than MG-PSZ. Best suited for application