Ultrasonic Evaluation of Ceramics With Micro-Cracks

Materials used in high-pressure vessels may be subjected to rapid temperature change, which may induce micro-cracks on the surface and into material. The growth of micro-cracks is detrimental to facility life. Chromium carbide (Cr₃C₂) has been proved to be a potential structural material for toughening alumina in biomedical and industrial applications because of its high Young’s modulus and erosion resistance. On the other hand, TiC/Al₂O₃ composite has been used as a magnetic head slider due to its good wear resistance and mechanical strength, and potentially could be an excellent lining material. In this study we thermally shocked ceramic material in disc shape to create different degrees of micro-cracking and use ultrasound attenuation technique to evaluate the damage. This includes narrow band tone burst at different frequency. The results showed significant dependence between ultrasonic attenuation and shock temperature. Corresponding SEM pictures show although the size of micro-crack doesn’t change, the depth of the micro-cracks increases. It is demonstrated that ultrasonic attenuation proves to be a reliable tool for evaluating micro-fractures in solids.