Qiao Guanjun

Preparation and Interface Structures of Metal-encased SiC Composite Armors with Interpenetrating Structure

Abstract A novel type of ceramic composite armor, metal-encased SiC ceramic armor with interpenetrating structure, was fabricated using a composite process, including preparation of reaction bonded SiC ceramic plate with ordered holes and metal casting of the macro-porous ceramic plate. The interface microstructures and elemental distributions or compositions of three different metals (a steel and two Ti alloys)/SiC composite armors were analyzed by scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). Relatively good interfacial bonding between ceramic and metal components was obtained, which is closely related to interfacial interactions and compressive residual stress on the ceramic during the cooling stage of casting. The interface microstructures depend significantly on the metal component composition (including the main element and the state of its existence after casting) and the casting process.

Mechanical and environmental factors in the cyclic and static fatigue of a machinable glass-ceramic

Abstract The effects of environment on cyclic and static fatigue behaviour were investigated with a machinable glass-ceramic and its original glass. Tests were conducted at ambient temperatures in three environments, i.e. moist air, distilled water and kerosene, and an indentation/bending technique was used. The results indicate that cyclic loading increases crack growth rates of glass-ceramic in all the three environments, but it just has a negligible effect on the original glass. The two materials were very sensitive to the amount of water in the test environment. For static fatigue of the glass-ceramic, both the slopes of d a d t-K eff curves and their position along the abscissa varied with the environments, but under other conditions, only the position varied.

Interface and Wear Resistance of SiC Ceramic Column Grid Array Reinforced High-Chromium Cast Iron Composite Pretreated with TiH2

Abstract Reaction-bonded SiC ceramic columns were coated by titanium hydride (TiH2) powder paste firstly, and then pretreated in a vacuum at 1000 or 1400 oC for 20 min. After that, the pretreated SiC ceramic columns were fixed on a graphite plate. Subsequently, a kind of SiC ceramic column grid array reinforced high-chromium cast iron composites, with high macro-uniformity, reliability and designability of the ceramic reinforcements, were fabricated by metal casting. The microstructure analysis on the ceramic coating and the ceramic/metal interface of the SiC/iron composite reveals that a reliable metallic composite coating can be formed on the SiC surface after the pretreatment at 1400 oC which was proved to be a better pretreatment temperature. The as-formed coating would not be dissolved during the metal casting process, and the interfacial reactions between SiC and iron were also restrained effectively, resulting in an excellent ceramic/metal interface without delamination after wear testing. Moreover, the wear resistances of the SiC/iron composites with different SiC ceramic contents are improved markedly in comparison with that of the metal matrix due to the effective additions of SiC ceramic columns.