Effects of pellet surface roughness and pre-oxidation temperature on CMAS corrosion behavior of Ti2AlC

Abstract

Calcium-magnesium-alumina-silicate (CMAS) corrosion is a serious threat to thermal barrier coatings (TBCs). Ti2AlC has been proven to be a potential protection layer material for TBCs to resist CMAS corrosion. In this study, the effects of the pellet surface roughness and temperature on the microstructure of the pre-oxidation layer and CMAS corrosion behavior of Ti2AlC were investigated. The results revealed that pre-oxidation produced inner Al2O3 layer and outer TiO2 clusters on the pellet surfaces. The content of TiO2 decreased with decreasing pellet surface roughness and increased along with the pre-oxidation temperature. The thickness of Al2O3 layer is also positively related to the pre-oxidation temperature. The Ti2AlC pellets pre-oxidized at 1050 °C could effectively resist CMAS corrosion by promoting the crystallization of anorthite (CaAl2Si2O8) from the CMAS melt rapidly, and the resistance effectiveness increased with the pellet surface roughness. Additionally, the CMAS layer mainly spalled off at the interface of CaAl2Si2O8/Al2O3 layer after thermal cycling tests coupled with CMAS corrosion. The Al2O3 layer grown on the rough interface could combine with the pellets tightly during thermal cycling tests, which was attributed to obstruction of the rough interface to crack propagation.

CeO2 Protective Material against CMAS Attack for Thermal–Environmental Barrier Coating Applications

“…Based on the investigation on the interaction behavior of CMAS and CeO2, it could Based on the investigation on the interaction behavior of CMAS and CeO 2 , it could be found that CeO 2 is a useful material for mitigating CMAS attack to TBCs. Due to the excellent nucleating agent effect of the CeO 2 solid solution, one could design a T/EBC composition doped with Ce aiming to promote CMAS crystallization and suppress the melt penetration [49]. Meanwhile, based on the theory of optical basicity (OB), CeO 2 has a relatively moderate optical basicity (Λ = 1.01) compared to traditional TBC materials, which ensures that CeO 2 reacts with molten CMAS to form CeO 2 solid solution particles, promoting CMAS self-crystallization.…”

Design of Ti 2AlC/YSZ TBCs for more efficient in resisting CMAS attack

“…The Ti 2 AlC coatings are completely consumed after the CMAS corrosion for 6 h while the Ti 2 AlC pellets could resist the CMAS corrosion at the same temperature for 8 h without being destroyed [32]. When the Ti 2 AlC pellets contact with molten CMAS, a continuous inner Al 2 O 3 layer and a discontinuous outer TiO 2 layer can be formed on the surface [31,47]. According to the CaO-Al 2 O 3 -SiO 2 ternary phase diagram where the MgO content is 9 mol% from a study by Poerschke et al [48], as the Al 2 O 3 layer grows and dissolves into CMAS, the CMAS melt components adjacent to the Al 2 O 3 layer move from the liquid zone to the anorthite zone due to the Al enrichment, and TiO 2 exists as a solute in the CMAS melt with diffusion.…”

Enhanced oxidation resistance of HfB2‐SiC‐ZrSi2 coating at 1700°C through low‐loss film‐forming treatment

“…The defects generated during this process can provide a pathway for oxygen diffusion and cause oxidation damage to the carbon matrix 19,20 . Our previous work 21,22 has proved that low‐loss film‐forming treatment (LFT) based on reduced film‐forming temperatures can significantly reduce oxidation losses 23–26 . The glass layer formed in situ by LFT at low temperatures has stable structure and inhibits cracking between phases in the coating 27 .…”

“…19,20 Our previous work 21,22 has proved that low-loss film-forming treatment (LFT) based on reduced film-forming temperatures can significantly reduce oxidation losses. [23][24][25][26] The glass layer formed in situ by LFT at low temperatures has stable structure and inhibits cracking between phases in the coating. 27 Moreover, LFT can be accomplished in air environment without high temperature atmosphere and the cost is lower.…”