Impact Fracture Behavior of Turbine-Grade Silicon Nitride Ceramic Under Tensile Stress at Elevated Temperatures

Author(s):  
Hiro Yoshida ◽  
M. Munawar Chaudhri ◽  
Takero Fukudome ◽  
Sazo Tsuruzono

A series of particle impact tests was carried out at elevated temperatures up to 1400°C and under tensile stresses up to 200 MPa using a gas turbine-grade silicon nitride (SN282-Kyocera Corporation). It was found that: 1) At room temperature, 100 MPa tensile stress brings 8% strength degradation. 2) Regarding the effect of the temperature without applying tensile stress, similar to the case of quasi-static loading, the fracture toughness seems to play a predominant role under the dynamic loading also. 3) At 1350°C under 100 MPa tensile stress, effect of the stress on the degradation increases by 15%. 4) The effects of temperature and tensile stress on the strength degradation seem to be additive for temperatures up to 1350°C. Above 1350°C, remarkable strength degradation appears.

Author(s):  
Hiro Yoshida ◽  
Takashi Nakashima ◽  
Makoto Yoshida ◽  
Yasushi Hara ◽  
Toru Shimamori

A new high quality turbine system using monolithic silicon-nitride ceramic is under development. In this study particle impact tests of the silicon-nitride have been tried at room and elevated temperatures with and without tensile load, which simulates centrifugal force of blade rotation. In the experiment 1 mm diameter particle is impacted at velocities up to 900 m s−1. In this paper, critical velocities for bending fracture and Hertzian cracks are examined. Moreover, strength degradation at elevated temperature and spall fracture of the blade are discussed. The main results are: 1) The bending fracture mode critical impact velocity for soft particles is higher than that for hard particles. 2)The impact parameter ϕ for initiation of Hertzian cracks ranges 1.08×10−5 – 1.56×10−5 for the materials tested. 3)Strength degradation at elevated temperature was clearly observed. 4) In the impact tests on blades spall fracture, which was caused by interaction of stress waves, appeared.


2001 ◽  
Vol 16 (8) ◽  
pp. 2182-2185 ◽  
Author(s):  
Naoki Kondo ◽  
Yoshikazu Suzuki ◽  
Manuel E. Brito ◽  
Tatsuki Ohji

Tensile creep behavior of silicon nitride with aligned rodlike grains (anisotropic silicon nitride), fabricated by superplastic forging, was investigated at elevated temperatures. Creep rate of the anisotropic silicon nitride was about 1 order of magnitude lower than that of the isotropic one (without forging). The stress sensitivities for the isotropic and anisotropic specimens at 1200 °C were 2.1 and 2.6, respectively, and that for the anisotropic specimen at 1250 °C was 3.6. The grain alignment should cause a remarkable improvement in the creep resistance when a tensile stress is applied along the alignment direction.


2009 ◽  
Vol 42 (11-12) ◽  
pp. 1838-1845 ◽  
Author(s):  
J.L. Zhou ◽  
G.Q. Wu ◽  
W.N. Zhu ◽  
X.Y. Chen

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