Effect of C coating on the interfacial microstructure and properties of SiC fiber-reinforced Ti matrix composites

C coating of the SiC fiber critically influences the interfacial microstructure and properties of titanium matrix composites, and thus affects the overall composite properties. In this work, the interfacial microstructure and debond strength of SiC(C)/Ti–6Al–4V and SiC/Ti–6Al–4V composites was studied by comparison. The C coating prevented direct fiber–matrix interaction, and the interfacial reaction product for SiC(C)/Ti–6Al–4V composite was only TiC, comprising fine particles adjacent to the C coating and coarse particles adjacent to the matrix. At the interface of SiC/Ti–6Al–4V composite, a narrow layer of fine TiC particles was adjacent to the fiber, and a broad mixture layer of TiC and Ti5Si3 particles was adjacent to the matrix; the particle size increases gradually from the fiber to the matrix. C coating offered a weak interfacial bonding between the fiber and matrix, and the interfacial debond strength for SiC(C)/Ti–6Al–4V and SiC/Ti–6Al–4V composites was 118.2 ± 4.24 and 230 ± 6.28 MPa, respectively. Interfacial debonding occurred between the C coating and the reaction layer for the coated fiber composite, but between the fiber and the interface reaction layer for the naked fiber composite.