KJ Ceramics 31

Home | Program | Detailed Program

Detailed Program

Paper Number : ST-O05

Time Frame : 17:10~17:30

Presentation Date : Thurseday, 27, November

Session Name : Structural Ceramics

Session Chair 1# : Hai-Doo Kim

Session Chair 2# : Junich tatami

Slow Crack Growth Behavior of Yttrium Oxide from Static/dynamic Fatigue and Double Torsion Tests

Sung-Min LEE

Korea Institute of Ceramic Engineering and Technology

Yttria has been widely used in the semiconductor industry as a plasma facing material to F-containing plasma. It has been manufactured as sintered bulks or plasma-sprayed coatings. However, ceramic industry has experiences of unexpected failure during the application of the parts made of yttria. Large sintered parts were reported to break randomly during their applications without any determined lifetime. However, causes were not clear and some weakness due to thermal shock was inferred without evidences. In this stduy, we tried to approach this unpredictable failure from the aspects of the slow crack growth. To the authors’ knowledge, slow-crack growth behavior of yttria ceramics has not been reported yet. We used various techniques including static and dynamic fatigue and double torsion tests. In dynamic test, Vickers indents were made on the specimens to introduce artificial flaw and compare the results with those from machined specimens. We found very strong sensitivity of yttria ceramics to humidity with stress exponent of around 21 after considering residual stress effect from indentation (Fig 1). From double torsion experiment we obtained quantitative crack growth rate as functions of the stress intensity factor and humidity level. The crack growth rate was effectively zero under mineral oil and very fast inside water with threshold stress intensity factor of around 0.7 MPam0.5. The threshold value was around 50% of critical stress intensity factor, showing strong sensitivity of yttria ceramics to humid environment.

Figure 1 Strength Variation of yttria as a function of stressing rate inside oil or air.

References:

[1] A. Shyam and E. Lara-Curzio, J. Mater. Sci., 41 (2006) 4093.

Acknowledgements :

Back Home