X-ray residual stress measurement of sintered Si3N4.

Abstract

In the case of strength design of ceramic parts, it is important to consider residual stress. The purpose of this study is to solve some problems related to such residual stress in ceramics.The residual stress on the Si3N4 surface prepared with several different treatments was measured by X-ray technique using a prototype Vanadium X-ray tube. V-radiation is suitable for getting a strong diffraction profile at a high diffraction angle and a shallow effective penetration depth for Si3N4. A new method developed by Yoshioka et al. was employed for analysis. In this method of analysis, the residual stress just on the surface and the stress gradient can be calculated. As a result, high compressive surface residual stress up to 1165MPa and the stress gradient of 154MPa/μm were observed on the heavily ground surface. In the case of the surface polished with wet cloth, the residual stress was -111--141MPa and the stress gradient was 14-27MPa/μm. When the above values are compared with the values obtained from the ordinary sin2ψ method, it is clear that the stress gradient near the surface must be taken into account in these cases. In order to evaluate the depth of the deformed layer of a surface ground with the cutting depth of 15μm, the residual stress was measured every time after the surface was removed by 2μm each by sputtering technique. When the surface was removed up to 8μm, the residual stress became undetectible and the half value breadth of diffraction profile converged to a constant value. It was concluded that the depth of the deformed layer of the ground surface was 8μm. Finally, it was made clear that the effective penetration depth of the V-radiation is shallow enough to evaluate the residual stress on the ground Si3N4 specimen.