Comprehensive study on the microstructure evolution and oxidation resistance performance of NiCoCrAlYTa coating during isothermal oxidation at High temperature

• Published in: Corrosion science Vol. 175; p. 108889
• Main Authors: Yang, Hong-Zhi, Zou, Jian-Peng, Shi, Qian, Wang, Di, Dai, Ming-Jiang, Lin, Song-Sheng, Chen, Xuanxuan, Wang, Wei, Xia, Xiao-Ping
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Ltd 01.10.2020; Elsevier BV
• Subjects: Aluminum oxide; Crack propagation; Cracks; Diffusion coating; Dominant mechanism; Evolution; Failure mechanisms; High temperature; High temperature oxidation resistance; Interdiffusion; Internal oxidation; Microstructure; Microstructure evolution; NiCoCrAlYTa coating; Oxidation; Oxidation resistance; Reaction kinetics; Scale (corrosion); Temperature dependence; NiCoCrAlYTa coating; High temperature oxidation resistance; Dominant mechanism; Microstructure evolution
• ISSN: 0010-938X; 1879-0496
• DOI: 10.1016/j.corsci.2020.108889

•The internal oxidation roughens the oxides scale/coating interface and benefits the formation of the spinels, causing the delamination of the oxides scale and nucleation of the cracks.•The corresponding oxidation rate constant of NiCoCrAlYTa coating after oxidation at 1050℃ is 6.27×10−4 mg2 cm-4 h-1, which is reduced two or three orders of magnitude compared to that of the coating after oxidation at 1100℃ (2.88×10-2 mg2 cm-4 h-1) and 1150℃ (1.35×10-1 mg2 cm-4 h-1), indicating the coating can hardly work at high temperature above 1100 for the long term oxidation.•Based on the result of calculated diffusion activation energy, the failure mechanism of NiCoCrAlYTa coating is largely dependent on the exposure temperature. During the growth of oxides scale, the external diffusion of cations is the mainly process, accompanied with the internal diffusion of oxygen to a certain degree. The microstructural evolution and high temperature oxidation resistance performance of NiCoCrAlYTa coating were investigated via isothermal oxidation at 1100℃ and 1150℃ for up to 200 h. The results reveal that the microstructure of oxides scale formed at higher temperature gradually evolve from a dense alumina layer to a mixed oxide layer, consisting of α-Al2O3 and considerable amount of NiAl2O4 spinel, NiO as well as abundant amount of (Y, Ta)-enriched oxides, which not only caused the formation of defects, such as voids and cracks, but also developed a rumpling of coating surface, accelerating the aggregation and growth of cracks. And serious internal oxidation was also detected as the oxidation time increased, which was discussed and explained from the aspect of interdiffusion behavior. At high temperature of 1100℃ and 1150℃, the oxidation kinetics curve deviated from parabolic law, indicating the oxidation resistance property of NiCoCrAlYTa coating compromised under these severe conditions. Based on the result of calculated diffusion activation energy, the failure mechanism of NiCoCrAlYTa coating is largely dependent on the exposure temperature. During the growth of oxides scale, the external diffusion of cations is the mainly process, accompanied with the internal diffusion of oxygen to a certain degree. The results could provide comprehensive understanding of the microstructural evolution during oxidation, which was essential for controlling oxides scale growth and improving the durability of NiCoCrAlYTa coating.