Strength Distributions of SiC Ceramics After Oxidation and Oxidation Under Load

Abstract

The room-temperature strength distributims of a sintered and a hot-pressed S i c were examined as-machined, after oxidation at 1370"C, and after oxidation under load at 1370°C. The strengths were observed to be dependent on both the duration of oxidation and the magnitude of the applied load. Processes resulting in both strengthening and weakening behavior were observed to occur, at times simultaneously within the same strength distribution. This dynamic situation indicates that the strength-controlling flaw populations are highly transient in nature.

Oxidation and Strength Retention of Monolithic Si3N4 and Nanocomposite Si3N4‐SiC with Yb2O3 as a Sintering Aid

“…Whenever the oxide layer became thicker, the crack blunting effect was negated by the generation of new defects, either within the oxide scale or at the interface between the substrate and the oxide scale. [22][23][24][25][26][27] Thus, when the oxidation temperature was 1400°and 1500°C, the strength retention decreased slightly (2.5% and 15%, respectively) as a result of the formation of thick oxide layers.…”

Corrosion characteristics of silicon carbide and silicon nitride

“…Passive oxidation could, in fact, have a beneficial effect by healing surface cracks and increasing the average flexural strength, while active oxidation could lead to new surface flaws that would decrease the average flexural strength [39]. The roles of material processing and composition were found to be important factors for both the distribution of strength [40], Tables 6 and 7, and the retention of strength, Fig. 5, under long-term exposures to oxidizing environments [41].…”

Oxidation kinetics strength of Hi‐NicalonTM‐S SiC fiber after oxidation in dry and wet air

“…Recent work has shown that ~100 nm SiO 2 glass scales increase SiC fiber strength for near‐stoichiometric SiC fibers such as Hi‐Nicalon™‐S, but thicker, crystallized scales degrade strength. Ambiguous effects of oxidation on SiC strength have been observed for bulk material …”

“…Ambiguous effects of oxidation on SiC strength have been observed for bulk material. 57,58 Single filament tensile strengths are measured for Hi-Nicalon TM -S SiC fiber after oxidation for up to 100 hours in dry and wet air at 700°C-1400°C. Preliminary results were presented elsewhere.…”