NEW HIGH-STRENGTH ZIRCONIA FOR AUTOMOTIVE ENGINE COMPONENTS, OTHER HIGH PERFORMANCE PARTS
13 August 2003 - Carpenter Technology Corporation

The new ZrX-GBP (grain boundary pinned) grade developed by Carpenter Advanced Ceramics is considered an important advance in zirconia technology, providing bending strength significantly higher than that of other commercially available Mg-PSZ materials. Its flexural strength is 850 MPa at 20°C, well above that of 620 MPa for the TS (thermal shock) grade and 725 MPa for the MS (mechanical strength) grade at the same temperature. Both the TS and MS are grades of Mg-PSZ. Carpenter’s new ZrX-GBP zirconia has flexural strength approaching that of traditional Y-TZP, but with higher fracture toughness and without the thermodynamic instability and high temperature creep problems associated with that grade.

ZrX-GBP zirconia, exhibiting no hysteresis during heating and cooling, can provide a two-micron tight fit unaffected by thermal expansion. This property allows close tolerance, high pressure applications with metal components.

Carpenter Advanced Ceramics, the subsidiary of Carpenter Technology Corp., Reading, Pa., that produces the material, reports that the mean coefficient of thermal expansion for its newly developed zirconia material over a temperature range of 25 to 400°C is 10x10-6/°C. This is comparable to that of metal, and distinctly higher than the 6x10-6/°C for most ceramics.

The flexural strength of the new ZrX-GBP zirconia grade is higher than that of any of the known Mg-PSZ materials due to development of a highly engineered microstructure. The very fine average grain size attained, together with a new technology for inhibiting grain growth and boundary movement, contribute greatly to the grade’s high strength and impact resistance.

Average grain size of the new zirconia ranges between 20 and 30 microns, depending on the application. Grain size averages 40 microns for the MS grade, and averages 45 microns for the TS grade.

ZrX-GBP zirconia has the same excellent corrosion resistance and overall stability as Carpenter’s MS and TS grades of Mg-PSZ zirconia. The new grade also has excellent resistance to galling, scuffing and wear in sliding contact with steels and other metals.

U.S. and international patents are pending.

http://www.cartech.com

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