High temperature dynamic fatigue performance of a hot isostatically pressed silicon nitride

Silicon Nitride for High‐Temperature Applications

“…The materials showed comparable creep properties in the same order of magnitude 74 . Furthermore, the SCG behavior of the SiO 2 ‐rich material (SiO 2 /Y 2 O 3 ratio of 2.12) seems to be comparable to the stress oxidation zone reported by Wereszczak et al 52–55 Whereas the amount of the grain‐boundary phase was different (5–6 vol% in NT 154 and 164, 10.5 vol% in the hot pressed material) the grain‐boundary phase composition with a SiO 2 /Y 2 O 3 ratio of >2 in both materials was nearly similar. In this way, the composition of crystalline and residual amorphous grain‐boundary phase seems to be more important than their overall amount in the sintering additive containing Si 3 N 4 , similar to the tendency described above for Si 3 N 4 without sintering additives.…”

“…A first group with a comprehensive mechanical characterization is represented by various HIP qualities with only a small amount of Y 2 O 3 (4–6 wt%). Typical materials described in the literature 39–55 are…”

“… NT 154 (Norton, Norton Advanced Ceramics, Northboro, MA) 4 wt% Y 2 O 3 , α/δ Y 2 Si 2 O 7 and some apatite phase Y 5 (SiO 4 )N, 39–44 NT 164 (Norton) 4 wt% Y 2 O 3 (higher SiO 2 amount forming Si 2 ON 2 , 30–40% residual α‐Si 3 N 4 , 45,46 NCX‐5102 (Norton) 4 wt% Y 2 O 3 , higher amount of α‐Si 3 N 4 , only γ‐Y 2 Si 2 O 7 , 47,48 PY6 (GTE Laboratories, Inc., Waltham, MA) 6 wt% Y 2 O 3 , Y 2 Si 2 O 7 48–52 …”

“…The oxidation of the materials occurred on both the surface and in the upper bulk of the materials consequently leading to changes in the microstructure of the upper region of the bulk material. Wereszczak et al 52–55 described a clear evidence of such oxidation effects in these materials in combination with tensile stress at temperatures >1300°C resulting in a stress corrosion cracking zone influencing the mechanical behavior of these materials.…”

“…A first group with a comprehensive mechanical characterization is represented by various HIP qualities with only a small amount of Y 2 O 3 (4-6 wt%). Typical materials described in the literature 39 [48][49][50][51][52] There were two purposes in using these compositions. The first was to obtain better high-temperature mechanical properties with a minimal amount of sintering additives similar to studies in other groups.…”