|Budget Amount *help
¥3,300,000 (Direct Cost : ¥3,300,000)
Fiscal Year 1999 : ¥800,000 (Direct Cost : ¥800,000)
Fiscal Year 1998 : ¥2,500,000 (Direct Cost : ¥2,500,000)
From fiscal 1998 until fiscal 1999, a dynamic environmental evaluation was performed on the interface of ceramic-metals joints. The following results were obtained:
1. Dynamic environmental evaluation
The test specimens were subjected to three-point bending, four-point bending, and cyclic loading tests conducted in heat, vacuum, and gas atmosphere. The joints of the test specimens were strong enough to withstand the test environments.
2. Fixed load/Thermal loading test (Si3N4-kovar joints prepared by the active metallic method)
(1) When the joints were thermally loaded under a fixed load of 204 MP.a at 86.4 ks in a temperature range of 323-573K, the fracture strength decreased from 450 Mpa almost linearly as the test temperature increased.
(2) In terms of morphology, joints under thermal load caused Si3N4 to adhere to the koval alloy side. The size of the Si3N4 adhering area started to decrease when under load at a test temperature of 423K and the fracture strength also decreased accordingl
(3) The joints fractured at the interface of the Si3N4 and Ti-compound (TiN, Ti5Si3) reaction layer.
(4) When the test temperature increased, the fracture strength decreased. This is thought to have occurred because the thermal loading increased the shear stress, which can be attributed to the discrepancy in the thermal expansion rate at the interface of the Si3N4 and Ti-compound (TiN, Ti5Si3) reaction layer.
3. Cyclic loading/Thermal loading test (Si3N4-kovar joints prepared by the active metallic method)
(1) The joints were thermally loaded to 398K under cyclic loading of 204 Mpa However, the fracture strength did not show any characteristic tendency even when the number of cycles was increased. Thermal loading to 448K under cyclic loading of 204 Mpa did not reduce the fracture strength remarkably, irrespective of the number of cycles. This is thought to result from softening of the brazing layer due to heating, which released residual stress from the joint and the resulting plastic deformation of the joint absorbed the load.
These results clarify the environmental conditions [Suggest: required] for practical use of ceramic-metallic joints. However, testing under higher stress and thermal loads is deemed to be necessary. Less