Influence of Supersaturation on Growth Behavior and Mechanical Properties of Polycrystalline 3C-SiC on W Wire Substrate

Abstract

As an important reinforcement for metal matrix composites, the microstructure and mechanical properties of W-core SiC filament have drawn increasing attentions among researchers. In this work, the growth behavior of polycrystalline 3C-SiC on W-wire substrate in the chemical vapor deposition (CVD) process and the evolution of mechanical properties in preparation of W-core SiC filament, were investigated as a function of gas-phase supersaturation. Kinetic studies revealed that the growth of 3C-SiC grains was limited by surface reactions at both 850 °C and 1050 °C, and the deposit experienced similar morphological changes from a porous structure to large clusters, with the increase in supersaturation. Structural analyses and mechanical tests show that the production of pores and the amorphous phase with a low supersaturation, of 9.6 × 107 at 850 °C, resulted in a reduction in the modulus and hardness of the polycrystalline deposits, to 270.3 GPa and 33.9 GPa, while the reduced structural defects (e.g., stacking faults and twins) in highly (111) orientated 3C-SiC grains, as well as the improved surface quality obtained with the medium supersaturation of 1.6 × 107 at 1050 °C, enhanced the tensile strength and the Weibull modulus of W-core SiC filament to 2.88 GPa and 11.2, respectively. During the growth of 3C-SiC grains, the variation in structural defects density is controlled by the critical nucleation energy of the two-dimensional (2D) nucleus.