Microstructural and mechanical characteristics of SiC/SiC composites with modified-RS process

This paper deals with the efficiency of modified-reaction sintering techniques including a impregnation pressure and a cold pressure as well as the applicability of new high performance fiber, in order to develop high performance SiC/SiC composites. SiC/BN coated Hi-Nicalon fiber, SiC coated Tyranno ZMI fiber and Tyranno SA fiber were used in this composite system. Microstructural characteristics of reaction sintered SiC/SiC composites were investigated by means of SEM, EDS and TEM. Mechanical properties and fracture mechanisms of SiC/SiC composites were also evaluated through the three-point bending test. Improved SiC/SiC composites with high density and high strength were successfully fabricated by the sequential application of low pressure impregnation and cold pressing processes. An excellent chemical stability of Tyranno SA fiber during the reaction sintering process was also revealed. Tyranno SA fiber reinforced SiC/SiC composites with no interfacial coating exhibited good flexural strength and elastic modulus, compared to those reinforced by BN/SiC coated Hi-Nicalon and SiC coated Tyranno ZMI fibers. However, this composite system needed an appropriate interfacial coating for proper CMC composite behavior.