A new methodology to guarantee the structural integrity of Al₂O₃/SiC composite using crack healing and a proof test

Abstract

A B S T R A C T Structural ceramics are brittle and sensitive to flaws. As a result, the structural integrity of a ceramic component may be seriously affected by inherent flaws. Self-crack-healing is an excellent answer to this problem. At the moment, however, there is no technique to heal embedded flaws. Therefore, a technique to guarantee the reliability of ceramic components is demanded, and thus a technique using crack healing followed by proof test was developed by K. Ando et al. to accomplish this. With this technique, testing the mechanical behaviour of the crack-healed zone is very important for ensuring the structural integrity of a ceramic component. In this study, first Al 2 O 3 /SiC composite with an excellent crack-healing ability was sintered. Second, a crack was introduced on the sample (3 mm × 4 mm × 36 mm), which reduced the bending strength by about 80%, and subsequently the crack was healed. Third, a proof test was carried out on the crackhealed sample. Last, using the crack-healed and proof-tested sample, a fracture test was carried out up to 1373 K. The measured minimum fracture stress (σ Fmin ) was compared with the theoretical minimum strength (σ G ) from room temperature (R.T.) to 1373 K. It was concluded that σ G showed good agreement with σ Fmin up to 1373 K and that the crack healing followed by proof test was an excellent technique to increase the survival probability by administering a proof test and to guarantee the reliability of Al 2 O 3 /SiC composite.

On the use of TiC as high-temperature healing particles in alumina based composites

“…According to previous studies [3,4], 15 vol.% fraction of SiC was sufficient for filling the surface crack with 100 m and attain full strength recovery of alumina/SiC composite. Assuming the local crack facing distance of the induced indentation cracks to be the same one can argue that the optimal volume fraction of TiC selfhealing agent should be of the order of 30 vol.% in order to realize a comparable self-healing of TiC/alumina composite and to compensate for the lower RVE value.…”

“…However, they also noted that the formed SiO 2 could not seal the pre-cracks fully due to the low SiC particle content. Ando et al were the first to report in detail on the self-healing behaviour of SiC particles containing alumina matrix composites as a function of temperature and annealing time [3][4][5]. It was shown that alumina/15 vol.%-SiC composites can attain a complete strength recovery by annealing in air at 1300 • C for 1 h or at 1200 • C for 10 h [3].…”

Crack-Healing Ability of Structural Ceramics and Methodology to Guarantee the Reliability of Ceramic Components

“…Figure 20 shows the data on the fracture stress of the crack-healed and the proof-tested specimens as a function of temperature with the evaluated σ G for the crack-healed alumina/20 vol% SiC particles composite when σ p = 435 MPa (Ono et al, 2007). Except the data at 1373 K, all specimens have higher strength than the σ G at all temperatures.…”

The effect of the TiC particle size on the preferred oxidation temperature for self-healing of oxide ceramic matrix materials

“…Of course, the required minimal temperature to trigger the healing reaction depends primarily on the chemical stability of the healing material in an oxygen-containing environment. This dependence has already been demonstrated (but apparently not been appreciated) in the combined first-generation studies on self-healing of Al 2 O 3 or Si 3 N 4 filled with SiC or Ni particles [3][4][5][6][7]. In these studies, the crack healing ability was studied as a function of both temperature (from 900 to 1400°C) and time (between 1 and 300 h) and widely different values were obtained for different particle sizes.…”