Corrosion of Nonoxide Silicon‐Based Ceramics in a Gas Turbine Environment

Silicon Nitride for High‐Temperature Applications

“…Models in order to assess the recession rate have been provided by Opila et al 173 and Yuri et al 175 In experimental studies, recession rates of 41 mm/h were found for advanced Si 3 N 4 and SiC materials destroying the materials after serve in application-relevant times (410 000 h) in hot gas environments. [174][175][176][177][178][179][180] A weight loss of about 8 wt% observed after high pressure burner rig tests at 14001C (P 5 5 bar, v 5 50 m/s, P H2O 5 0.9 bar) resulted in a material loss from the surface of about 70 mm after 100 h. After an application relevant time of about 10 000 h an unacceptably high material loss of about 7 mm would be found. 179 Hence, EBCs are presented to be the solution to protect the Si 3 N 4 from corrosive environments at high temperatures, preventing the corrosion attack of the water vapor in the hot gas atmosphere.…”

“…[174][175][176][177][178][179][180] A weight loss of about 8 wt% observed after high pressure burner rig tests at 14001C (P 5 5 bar, v 5 50 m/s, P H2O 5 0.9 bar) resulted in a material loss from the surface of about 70 mm after 100 h. After an application relevant time of about 10 000 h an unacceptably high material loss of about 7 mm would be found. 179 Hence, EBCs are presented to be the solution to protect the Si 3 N 4 from corrosive environments at high temperatures, preventing the corrosion attack of the water vapor in the hot gas atmosphere. Several factors have to be considered during the development of an EBC system:…”

“…However, one main problem preventing silicon-based nonoxide ceramics like Si 3 N 4 from being applied in gas turbines were found to be the corrosion processes; especially the reaction with the water vapor leads to surface recession and, therefore, dimensional changes of the ceramic component occur. [169][170][171][172][173][174][175][176][177][178][179][180][181] High water vapor pressure in combination with high Sidebar 3. Requirements for Industrial Application In the course of the development of high-temperature Si 3 N 4 one should pay strict attention to the aspects and requirements of an industrial production.…”

Degradation of Silicon Nitride Glow Plugs in Various Environments Part 1: dc Electric Field in Ambient Air

“…While oxidation of Si 3 N 4 ‐based ceramics in dry air and oxygen was extensively studied, 1–5 it is known that silicon nitride oxidizes up to an order of magnitude faster in wet than in dry oxygen and the mechanism changes from parabolic to paralinear 6–12 . Additionally, the swings of oxidizing/reducing conditions in combustion environments can affect the stability of the silicate film on the component's surface; numerous studies have focused on the corrosion of silicon‐based ceramics under these complex combustion conditions 13–20 . The need to protect nonoxide structural ceramics in such combustion environments, including gas turbines, triggered an active search for “Environmental Barrier Coatings” that could prevent (or slow down) the degradation of such components in oxidizing/reducing conditions including water vapor 21–26 .…”

“…[6][7][8][9][10][11][12] Additionally, the swings of oxidizing/reducing conditions in combustion environments can affect the stability of the silicate film on the component's surface; numerous studies have focused on the corrosion of silicon-based ceramics under these complex combustion conditions. [13][14][15][16][17][18][19][20] The need to protect nonoxide structural ceramics in such combustion environments, including gas turbines, triggered an active search for ''Environmental Barrier Coatings'' that could prevent (or slow down) the degradation of such components in oxidizing/reducing conditions including water vapor. [21][22][23][24][25][26] The additional damage mode for Si 3 N 4 -based ceramic heaters of GP is the degradation of the internal structure of the ceramic heater due to the applied electrical current.…”