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The effect of platinum (a rare metal)–aluminide coating parameters on the tensile properties of nickel-based superalloy Rene®80 was evaluated at 871 °C. For this purpose, initial layers of platinum with different thicknesses (2, 4, 6 and 8 μm) were coated on tensile samples. Then, low-temperature high-activity (LTHA) and high-temperature low-activity (HTLA) processes were used for aluminizing. Results of microstructural evaluations using scanning electron microscope (SEM) and phase analysis by X-ray diffraction (XRD) showed a three-layer structure coating for different platinum layer thicknesses and both aluminizing processes. Increasing the thickness of the platinum layer from 2 to 8 μm led to the improvement in the final coating thickness from 91.6 to 102.1 μm in HTLA. This increase was from 128.1 to 148.6 μm in LTHA. The results of hot tensile tests at 871 °C showed a decrease in strength properties of the coated samples compared to the uncoated ones. However, HTLA and high thicknesses of the initial platinum layer showed an intense reduction. The results of fractographic evaluations about uncoated samples showed a ductile fracture. On the other hand, coated samples showed a simultaneous ductile and brittle fracture failure mechanism. But the main fracture morphology was brittle cleavage fracture which was for the HTLA. [ABSTRACT FROM AUTHOR]

In this study, tungsten–copper (W–Cu) composite was fabricated using the sintering process to examine the corrosion, wear and hardness of the fabricated samples at three different temperatures of 1050, 1150 and 1300 °C. The potentiodynamic polarization behavior of the composite samples was evaluated in 3.5% NaCl solution containing different benzotriazole inhibitors. Finally, the microstructure of the W–Cu composite was examined by SEM, TEM, XRD and EDS analyses. The XRD results on the milled samples showed that the optimal conditions were obtained with a ball to powder ratio of 16:1 and a milling time of 15 h, so that the crystals with a size of 16.76 nm were obtained. Also, the highest hardness (185 HV) and relative density (97.34%) were obtained in the samples sintered at 1300 °C. With increasing the wear force, the work hardening increased in the mechanically mixed layer, which led to a rise in the wear rate and a decrease in the friction coefficient. The corrosion behavior of the composite indicated that by addition of 200 ppm inhibitor in the corrosion solution, the corrosion current density decreased from 3.73 to 0.59 μA/cm2 and the corrosion potential improved from − 630.46 to − 336.28 mVSCE. [ABSTRACT FROM AUTHOR]

The main purpose of this work is to optimize the mechanical properties of tungsten–copper (W–Cu) nanocomposite fabricated by the sintering process. For this purpose, the parameters of sintering temperature, sintering time and weight percentage of copper were selected to optimize the compression strength, impact strength, hardness and corrosion resistance of the W–Cu nanocomposite using the desirability function procedure and response surface method. The analyses of transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) were also performed to examine the microstructure of W–Cu nanocomposite. The results exhibited that a rise in the sintering temperature from 1000∘C to 1150∘C significantly enhanced the impact strength of W–Cu nanocomposite, while a rise in the sintering temperature from 1150∘C to 1300∘C deteriorated the impact strength. Moreover, the compression strength and hardness of the W–Cu nanocomposite continuously improved by elevation of sintering temperature from 1000∘C to 1300∘C. A rise in the amount of Cu from 20 wt.% to 40 wt.% led to a reduction in the hardness of the W–Cu nanocomposite, while a rise of Cu content improved the impact and compression strengths. The results also indicated that the mechanical properties of W–Cu nanocomposite enhanced simultaneously by using 27 wt.% Cu at sintering temperature of 1197∘C and sintering time of 2.7 h. The samples sintered at the optimal conditions indicated a higher corrosion resistance than that sintered at the initial conditions. [ABSTRACT FROM AUTHOR]