Radio frequency-assisted zirconium carbide matrix deposition for continuous fiber-reinforced ultra high temperature ceramic matrix composites

Zirconium carbide (ZrC) is considered to be a potential candidate for ultra high temperature applications due to its high melting point, good chemical inertness, and ablation resistance, but the monolithic form suffers from low fracture toughness and hence poor thermal shock resistance. Reinforcing it using continuous carbon fibers (Cf) to create an ultra high temperature ceramic matrix composite is an obvious solution, however densifying ZrC requires the use of very high temperatures combined with significant pressure, such as obtained by using hot pressing or spark plasma sintering, which risks damaging fibers. In the present work, radio frequency-assisted chemical vapor infiltration (RF-CVI) has been investigated with a view to forming Cf/ZrC composites. These initial experiments revealed the ability to deposit pure, nano-grained, and near stoichiometric ZrC with deposition occurring preferentially from the center of the sample due to the nature of the inverse temperature profile developed. The deposited ZrC grains were in the range of 4–9 nm in size and had a lattice parameter of 0.4750 nm. The work also showed that the use of RF-CVI enabled the minimization of early pore sealing, a common problem for conventional CVI

Mechanical and Wear Behaviour of Hot-Pressed 304 stainless Steel Matrix Composites Containing TiB2 Particles

In the present article, mechanical and wear behaviour of hot-pressed 304 stainless steel matrix composites containing 2 and 4 vol% TiB2 particles was investigated. A density of over 92% was achieved at optimum hot-pressing temperature and TiB2 particles' content. Microhardness and yield strength of the composites were found to be improved remarkably as compared to their unreinforced counterpart. The enhancement of mechanical properties of the composites was discussed in light of their microstructural aspects and different possible strengthening mechanism models. Taylor strengthening was found to be dominant strengthening mechanism as compared to Orowan strengthening and load-bearing effect. Dry sliding wear behaviour was also investigated under load of 35 N at sliding speed 0.3 m/s. The wear resistance of the composites was found to be improved owing to uniform distribution of hard TiB2 particles. Based on our findings, it was concluded that processing parameters and amount of TiB2 have significant influence on mechanical and wear behaviour of steel matrix composites