Microstructure and interface thermal stability of C/Mo double-coated SiC fiber reinforced γ-TiAl matrix composites
(State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China)
Abstract: C/Mo duplex coating interfacially modified SiC fiber-reinforced g-TiAl matrix composite (SiCf/C/Mo/g-TiAl) was prepared by foil-fiber-foil method to investigate its interfacial modification effect. SiCf/C/TiAl composites were also prepared under the same processing condition for comparision. Both kinds of the composites were thermally exposed in vacuum at 800 and 900 °C for different durations in order to study thermal stability of the interfacial zone. With the aids of scanning electron microscope (SEM) and energy dispersive spectrometer (EDS), the interfacial microstructures of the composites were investigated. The results reveal that, although adding the Mo coating, the interfacial reaction product of the SiCf/C/Mo/TiAl composite is the same with that of the SiCf/C/TiAl composite, which is TiC/Ti2AlC between the coating and the matrix. However, C/Mo duplex coating is more efficient in hindering interfacial reaction than C single coating at 900 °C and below. In addition, a new layer of interfacial reaction product was found between Ti2AlC and the matrix after 900 °C, 200 h thermal exposure, which is rich in V and close to the chemical composition of B2 phase.
Key words: Mo coating; TiAl alloy; SiC fiber; titanium matrix composite; interfacial reaction; thermal stability