Effect of C/Mo duplex coating on the interface and mechanical properties of SiCf/Ti6Al4V composites

SiC fiber (with C/Mo duplex coating) reinforced Ti6Al4V-matrix composites were fabricated by vacuum hot pressing. Tensile property of the as-prepared composites was tested at room temperature. In order to study the interfacial thermal stability of the composites, vacuum thermal exposure of the as-prepared composites was carried out at 700 °C and 800 °C for different duration. The interfacial microstructure of the as-prepared and thermally-exposed composites was investigated by means of scanning electron microscope and energy dispersive spectrometer. The results indicate that the interfacial phase sequence of the as-prepared composite is SiC|C/Mo|TiC|Moresidual+β-Ti|β-Ti+α-Tiprimary|Ti6Al4V from SiC side to the matrix. The interfacial microstructure has no obvious evolution when the composites were thermally exposed at 700 °C, which indicates an excellent thermal stability of C/Mo duplex coating. Furthermore, there still exists C/Mo duplex coating at the interface when the composites were thermally exposed at 800 °C for up to 100 h. Therefore, the C/Mo duplex coating exhibits a more outstanding thermal stability than a single Mo coating at elevated temperatures below 800 °C. The tensile strength of the as-prepared composites was a little higher than that of the composites with only C coating, which should attribute to the good effect of the C/Mo duplex coating.