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New metal–ceramic laminated composites Ta/Ti3Al(Si)C2–TiC were obtained by spark plasma sintering. The samples were synthesized at a temperature of 1250°C and a pressure of 50 MPa for 5 min. For formation of the composites, preceramic paper with a powder filler based on the MAX phase of Ti3Al(Si)C2, as well as metal foils made of tantalum, were used. The phase composition, microstructure, and elemental composition were analyzed by X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray spectroscopy, respectively. It was found that as a result of sintering, dense multilayer composites were formed, consisting of tantalum metal layers, ceramic layers containing Ti3Al(Si)C2, TiC, and Al2O3 phases, as well as reaction layers ~13 μm thick at the metal–ceramic interface enriched with Ta, Al, and Si. Based on the mechanical test data, the ultimate bending strength of the obtained composites was determined (σbs = ~430 MPa). Metal–ceramic laminated composites with a refractory tantalum layer were shown to exhibit a ductile fracture mechanism accompanied by a more than fourfold increase in absolute deformation compared to a Ti3Al(Si)C2-based ceramic composite. This is achieved due to deflection, branching of cracks at the metal–ceramic interface, and plastic deformation of tantalum layers. [ABSTRACT FROM AUTHOR]

Structural and phase stability of the Pd-plated Ti3(Al, Si)C2–TiC composite at elevated temperatures was analyzed by the in situ X-ray diffraction method using synchrotron radiation. Porous Ti3(Al, Si)C2–TiC composite was prepared by spark plasma sintering of preceramic paper with 90 wt % of a Ti3(Al, Si)C2 powder filler at 1000°C and 20 MPa. The sintered composite was covered with a Pd film via electroless plating. During in situ investigation, the Pd-plated composite was linearly heated from 25 to 1000°C and annealed for 1 h at a maximum temperature. Structural and phase analysis reveals a formation of new Pd2Si, PdAl, and PdCx phases. It was noted that the newly formed phases began to be formed during heating at ~750°C. Scanning electron microscopy showed that the obtained Ti3AlSiC2–TiC composite had a well-developed porous structure where some pores were filled with Pd. After high-temperature treatment, Pd could be detected at depths up to 5 μm into the Ti3AlSiC2–TiC composite. [ABSTRACT FROM AUTHOR]

The effect of the crystal structure of the Mo sublayer on the resistance of the zirconium alloy Zr–1Nb with a Cr/Mo coating to high-temperature oxidation in air is studied. Three types of coatings are deposited by magnetron sputtering: single-layer Cr coating with a thickness of 8 µm and two-layer coatings with a sublayer of Mo (3 µm) of various textures and an outer protective layer of Cr (8 µm). Different textures of molybdenum films are formed by changing the configuration of the magnetron-sputtering system. Coated samples are oxidized in an atmospheric oven at 1100°C for 15, 30, 45, and 60 min. The results of X-ray-diffraction- and scanning-electron microscopy show that the use of a Mo sublayer limits the mutual diffusion of the Cr–Zr system. The diffusion of Mo leads to the formation of interdiffusion layers of Cr–Mo and Mo–Zr. Faster diffusion is observed at the Cr–Mo interface. The thickness of the residual Cr layer in two-layer coatings is greater than that in a single-layer coating under similar oxidation conditions. [ABSTRACT FROM AUTHOR]