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Coatings in a Zr-Mo-Si-B-N system were deposited by the magnetron sputtering of ZrB2-MoSi2 targets in argon and nitrogen. The structure of the coatings was investigated using scanning electron microscopy, X-ray diffraction, energy-dispersive spectroscopy, and glow-discharge optical emission spectroscopy. Mechanical and tribological properties were measured using nanoindentation and pin-on-disc testing. Oxidation resistance and oxidation kinetics were estimated via annealing in air at 1000–1500 °C and precision weight measurements. We found that the coatings deposited in Ar demonstrate a superior combination of properties, including hardness of 36 GPa, elastic recovery of 84%, a friction coefficient of 0.6, and oxidation resistance at temperatures up to 1200 °C. High oxidation resistance is realized due to the formation of the protective (SiO2 + ZrO2)/SiO2 oxide layer, which inhibits the diffusion of oxygen into the coating. [ABSTRACT FROM AUTHOR]

As part of the tests, a two-phase NiAl/Ni3Al alloy and a composite based on this alloy with 4 vol% addition of TiB2 were produced by the reactive FAST/SPS (Field Assisted Sintering Technology/Spark Plasma Sintering) sintering method. The sintering process was carried out at 1273 K for 30 s under an argon atmosphere. The effect of reactive SPS on the density, microstructure, and mechanical and tribological properties of a dual-phase Ni-Al intermetallic compound and Ni-Al-TiB2 composite was investigated. Products obtained were characterized by a high degree of sintering (over 99% of the theoretical density). The microstructure of sinters was characterized by a large diversity, mainly in regard to the structure of the dual-phase alloy (matrix). Compression tests showed satisfactory plastic properties of the manufactured materials, especially at high temperature (1073 K). For both materials at room temperature, the compressive strength was over 3 GPa. The stress–strain curves were observed to assume a different course for the matrix material and composite material, including differences in the maximum plastic flow stress depending on the test temperature. The brittle-to-ductile transition temperature was determined to be above 873 K. The research has revealed differences in the physical, mechanical and tribological properties of the produced sinters. However, the differences favourable for the composite were mostly the result of the addition of TiB2 ceramic particles uniformly distributed on grain boundaries. [ABSTRACT FROM AUTHOR]

Since obtaining a highly oriented structure based on a large-scale commercial ultra-high molecular weight polyethylene (UHMWPE) is considered very difficult due to its high molecular weight and melting index, modifying the structure of these cheap commercial UHMWPE brands into a supra-molecular structure with fiber-forming properties by adding a small amount of polyethylene wax (PE-wax) will provide the possibility to obtain highly oriented UHMWPE products with enhanced mechanical and tribological properties. In this work, highly oriented UHMWPE/PE-wax films were prepared. The PE-wax affected the UHMWPE as an intermolecular lubricant. The obtained lamellar structure of the UHMWPE/PE-wax composites had a better processability. The UHMWPE and UHMWPE/PE-wax structures for the xerogels and the films were studied by using differential scanning calorimetry and scanning electron microscopy. The PE-wax presence enhanced the mechanical properties of the UHMWPE/PE-wax films to a high degree. The highest average value of the tensile strength was 1320 MPa (an increase of 78%) obtained by adding a PE-wax content of 1.0 wt.%, and the highest average value of the Young's modulus was 56.8 GPa (an increase of 71%) obtained by adding a PE-wax content of 2.0 wt.%. The addition of the PE-wax increased the work of fracture values of the UHMWPE/PE-wax films up to 233%. The formation of the cavities was observed in the virgin UHMWPE films more than in the UHMWPE/PE-wax films, and the whitening of the oriented films was related to the crystallization process more than to the cavitation phenomenon. The coefficient of friction of the oriented UHMWPE/PE-wax films improved by 33% in comparison with the isotropic UHMWPE, and by 7% in comparison with the oriented virgin UHMWPE films. [ABSTRACT FROM AUTHOR]