Preparation of TiC-C Functionally Gradient Material (FGM) by Chemical Vapor Deposition

Abstract

Plate-like deposits having a compositional gradient from TiC-91. 5mol%C to TiC were obtained on a graphite substrate by chemical vapor deposition (CVD). The CVC conditions used were as follows; a TiCl₄-CH₄-H₂ system, a deposition temperature of 1673K, a total gas pressure of 1.3kPa, and a gas concentration ratio (mC/Ti) of 30.4 to 3.7. Cracks were observed in TiC-coated graphite (TiC NFGM), however, no crack in TiC/C FGMs. The cracking in TiC NFGM was thought to be due to the hoop and radial tensile stresses generated after CVD coating. Introduction of the C/TiC graded layer between the TiC layer and the substrate is effective to reduce the residual thermal stress.