Browsing by Publisher "University of Science and Technology Beijing"

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    Leaching kinetics of celestite in nitric acid solutions
    (University of Science and Technology Beijing, 2019) Kocan F.; Hicsonmez U.
    In this study, strontium nitrate extraction from celestite in nitric acid solutions was investigated using the leaching method. The influences of acid concentration, solid-to-liquid ratio, stirring speed, and reaction temperature on the leaching of strontium from celestite concentrate were studied. The results showed that the leaching rate increased with increasing acid concentration, stirring speed, and temperature and decreased with increasing solid-to-liquid ratio. The particle size was fixed in all of the dissolution experiments. The results showed that the stirring speed and the temperature were the most influential parameters with respect to the leaching process. The kinetic model best fit control by diffusion through the product layer. The activation energy of the dissolution celestite in nitric acid solutions was calculated to be 42.22 kJ/mol. © 2019, University of Science and Technology Beijing and Springer-Verlag GmbH Germany, part of Springer Nature.
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    Reliability evaluation of hardness test methods of hardfacing coatings with hypoeutectic and hypereutectic microstructures
    (University of Science and Technology Beijing, 2019) Çömez N.; Çivi C.; Durmuş H.
    Hardfacing coatings involve hard carbide/boride phases dispersed in a relatively soft steel matrix. For the hardness measurements of hardfacing coatings, depending on the micro structure, both the hardness test method and the applied load affect the hardness results; therefore, they affect the wear performance predictions of the coating. For this reason, the proper hardness test method should be determined according to the microstructure of the coating, and the reliability of the obtained hardness data should be established. This study aimed to determine the most suitable hardness test method for hypoeutectic and hypereutectic microstructures of hardfacing coatings by analyzing the reliability of Rockwell-C and Vickers hardness test results. Reliability analyses showed that Rockwell-C is not a suitable hardness test method for hypereutectic hardfacing coatings. Based on the relationship between wear resistance and hardness, Vickers hardness method was found more suitable for the considered materials. © 2019, University of Science and Technology Beijing and Springer-Verlag GmbH Germany, part of Springer Nature.