Oxidation behavior and mechanical properties of C/SiC composites with Si-Mosi2 oxidation protection coating

• Published in: Journal of materials science Vol. 34; no. 24; pp. 6009 - 6014
• Main Authors: Xu, Yongdong, Cheng, Laifei, Zhang, Litong, Hongfeng Ying, Zhou, Wancheng
• Format: Journal Article
• Language: English
• Published: Heidelberg Springer 01.12.1999; Springer Nature B.V
• Subjects: Applied sciences; Building materials. Ceramics. Glasses; Carbon fiber reinforced plastics; Carbon fibers; Ceramic industries; Chemical industry and chemicals; Chemical reactions; Cracks; Diffusion layers; Exact sciences and technology; Fiber composites; Flexural strength; Materials science; Mechanical properties; Microcracks; Microstructural analysis; Molybdenum disilicides; Organic chemistry; Oxidation; Oxidation resistance; Oxygen; Protective coatings; Shock resistance; Silica glass; Silicon carbide; Silicon dioxide; Structural ceramics; Technical ceramics; Thermal resistance; Thermal shock; Weight; Coating material; Tridirectional fiber material; Mechanical properties; Thermomechanical properties; Experimental study; Composite material; Non oxide ceramics; Structural ceramic; Bending strength; Molybdenum Silicides; Silicon Carbides; Thermal shock resistance; Reaction mechanism; Oxidation; Silicon; Microstructure; Oxidation protection; Carbon fiber
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1023/A:1004741014185

A new kind of oxidation protection coating of Si-MoSi2 was developed for three dimensional carbon fiber reinforced silicon carbide composites which could be serviced upto 1550 °C. The overall oxidation behavior could be divided into three stages: (i) 500 °C < T < 800 °C, the oxidation mechanism was considered to be controlled by the chemical reaction between carbon and oxygen; (ii) 800 °C < T < 1100 °C, the oxidation of the composite was controlled by the diffusion of oxygen through the micro-cracks, and; (iii) T > 1100 °C, the oxidation of SiC became significant and was controlled by oxygen diffusion through the SiC layer. Microstructural analysis revealed that the oxidation protection coating had a three-layer structure: the out layer is oxidation layer of silica glass, the media layer is Si + MoSi2 layer, and the inside layer is SiC layer. The coated C/SiC composites exhibited excellent oxidation resistance and thermal shock resistance. After the composites annealed at 1550 °C for 50 h in air and 1550 °C ⇔ 100 °C thermal shock for 50 times, the flexural strength was maintained by 85% and 80% respectively. The relationship between oxidation weight change and flexural strength revealed the criteria for protection coating was that the maximum point of oxidation weight gain was the failure starting point for oxidation protection coating.