Search

ZrN and TiNiN nanolayers are alternately deposited on silicon substrate by magnetron sputtering. A series of ZrN/TiNiN nano-multilayer films with different Ni contents are prepared by varying the Ni:Ti volume ratio of the targets. The effects of Ni content on the microstructures and mechanical properties of ZrN/TiNiN nano-multilayer films are studied by X-ray diffractometer (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and nanoindentation instrument. The results show that with the increase of Ni content, the crystallization degree of ZrN phase first increases and then decreases. Besides, the hardness, elastic modulus and toughness of the films also increase first and then decrease with Ni content increasing. When Ni:Ti= 1:24, the ZrN/TiNiN nano-multilayer films obtain the highest hardness, elastic modulus and fracture toughness, which are 23.2 GPa, 317.8 GPa and 2.29 MPa·m1/2, respectively. This is mainly attributed to the best columnar crystal growth of the ZrN/TiNiN nano-multilayer film. The TiNiN layer changes into face centered cubic structure under the template of ZrN layer, and grows in coherent epitaxy with ZrN layer. ● A series of ZrN/TiNiN nano-multilayer films with different Ni contents are prepared by magnetron sputtering. ● When Ni:Ti= 1:24, the ZrN/TiNiN nano-multilayer films simultaneously obtain the highest hardness and fracture toughness. ● The high hardness and toughness are due to that the TiNiN layer grows in coherent epitaxy under the ZrN layer template. [ABSTRACT FROM AUTHOR]

In this work, the WC-Cr 2 (C, N)-Co nanocomposites were synthesized by using the one-pot carbothermal reduction nitridation hydrothermal precursor method. The preparation mechanisms, including phase and morphology evolutions, were investigated by differential thermal analysis (TG-DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and thermodynamic analysis. The results showed that phase evolution, with temperature increasing, follows the sequences of (amorphous phase, WO 2.72) → (CoWO 4 , WO 2.72 , WO 2 , CrWO 3) → (WO 2 , CoWO 4 , Co 6 W 6 C, CrWO 3) → (W 2 C, Co 3 W 3 C, WC) → (WC, W 2 C, Co 3 W 3 C) → (WC, Co, Co 3 W 3 C trace amount). Through comparing different heat treatment conditions, the powder particle size was more easily affected by temperature than holding time. The higher temperatures or longer time holding resulted in the aggregation of powder particles. Finally, WC-Cr 2 (C, N)-Co nanopowders with about 60 nm were obtained at 1050 °C for 1 h under the N 2 flow of 1 L/min with the oxygen content of 0.22 wt% and the free carbon content of 0.19 wt%. The TEM elements mapping revealed that Cr distributes uniformly with WC grains, Co and WC grains are combined well. The surface of WC-Cr 2 (C, N)-Co determined by XPS is mainly composed of W, Co, Cr, C, N, and O. The spark plasma sintering (SPS) sintered WC-Cr 2 (C, N)-Co composite shows a nanocrystalline microstructure with the average grain size ∼170 nm, and the excellent comprehensive mechanical properties with the Vickers hardness 1730 Kg·mm−2 and fracture toughness 11.5 MPa·m1/2, respectively. • The novel WC-Cr 2 (C, N)-Co nanocomposites were synthesized by using the one-pot carbothermal reduction nitridation hydrothermal precursor method. • The preparation mechanisms including phase and morphology evolutions, microstructure, chemical composition, and distribution were systematically investigated. • WC-Cr 2 (C, N)-Co nanopowders with about 60 nm were obtained at 1050 °C for 1 h under the N 2 flow of 1 L/min with oxygen content of 0.22 wt% and free carbon content of 0.19 wt%. • Through TEM and SEM characterization, the composition elements of the composite powder were evenly distributed, Co and WC grains are combined well. • Nano-WC-Cr 2 (C, N)-Co cemented carbides (∼ 170 nm) showed excellent comprehensive mechanical properties with Vickers hardness and fracture toughness of 1730 Kg mm−2 and 11.5 MPa m1/2, respectively. [ABSTRACT FROM AUTHOR]