Melt-infiltrated Composites Research Articles

Creep in vacuum of woven Sylramic-iBN melt-infiltrated composites

In order to better understand the effect of stressed-oxidation, the performance of woven Sylramic-iBN fiber-reinforced slurry cast melt-infiltrated (MI) composites were tested in creep and fatigue under non-oxidizing conditions. Initially creep and fatigue tests were performed at 1204 °C in an argon atmosphere; however, it was observed that sufficient oxidizing species existed in the environment to degrade the composites in a manner similar to air environments. Therefore, creep and fatigue tests were performed at 1204 °C in a vacuum environment which showed no evidence of oxidation and superior properties to composites subjected to stressed-oxidation conditions. The mechanical results and microscopy of the vacuum and argon are compared to the behavior of these composites tested in air. It was found that the stress-rupture properties of the vacuum-tested composites could be predicted from single fiber creep rupture data assuming reasonable values for the Weibull modulus.

Thermal ablation resistance of melt-infiltrated titanium diboride-(copper, nickel) composites

TiB 2/(Cu, Ni) melt-infiltrated composites with high ceramic volume fraction were prepared via powder pre-sintering and melt-infiltration processing in vacuum. Infiltrated TiB 2/(Cu, Ni) composite shows enhanced damage tolerance and good mechanical properties, i.e., fracture toughness up to 12.5 MPa m 0.5 and bending strength up to 844.7 MPa. The thermal shock and plasma ablation behavior of TiB 2/(Cu, Ni) composites were conducted by plasma arc heater. The initial microstructure, interfacial bonding and ablated morphology were investigated. The experimental results show that the ablation mechanism of TiB 2/(Cu, Ni) composites are mainly attributed to the transpiration cooling of metallic phase to bring away inner heat at elevated temperature. The microstructure analysis and properties measurement before and after ablation test reveals a clue of redistribution of infiltrated (Cu, Ni) so as to deduce and explain the functioning of transpiration cooling at ultra-high temperature.

Microstructural characterization and ablation mechanism of TiB 2/(Cu,Ni) melt-infiltrated ceramic composite

In this study TiB 2/(Cu,Ni) melt-infiltrated composites with the TiB 2 volume content of 81.6% were prepared by mean of pre-sintering of the as-pressed TiB 2 preform and melt-infiltration processing. The thermal ablation behavior of TiB 2/(Cu,Ni) composite was conducted by plasma arc heater. The microstructure, interfacial bonding and ablation behavior were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) pattern. The ablated morphology of cross-section includes three parts: ablated region, transition region and matrix region. The microstructure analysis after ablation experiment reveals a clue of redistribution of infiltrated (Cu,Ni) phase so as to analyze and explain the functioning of transpiration cooling.