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The Effect of pH on Slurry Erosion–Corrosion of Tungsten Carbide Overlays Alloyed with Ru

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Abstract

The aim of the study was to determine the effect of Ru additions to WC-Fe overlays when exposed to low pH slurry erosion conditions. These overlays were applied through Plasma Transferred Arc, and the original bulk Ru powder concentrations varied from 0.5 to 5 wt.%. A slurry jet impingement erosion–corrosion test rig was used to evaluate wear, and electrochemical measurements were performed to characterize the corrosion properties. The slurry mixtures contained silica sand and synthetic mine water. The pH was varied between 3 and 6.5 for the slurry erosion tests and lowered further for the corrosion characterization. Samples were examined optically and with a scanning electron microscope using energy-dispersive x-ray spectroscopy. X-ray diffraction analysis was used to determine the phases present. For the slurry erosion–corrosion results at the pH of 6.5, addition of Ru did not show a decrease in erosion–corrosion rates. However, when the pH was decreased to 3, by the addition of HCl, Ru improved the resistance. From the electrochemistry, it was also clear that Ru additions improved the corrosion resistance, but more than 1 wt.% Ru was required. At very low pH levels, the presence of Ru was not able to prevent corrosion.

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Acknowledgments

The authors gratefully acknowledge the financial assistance from the DST-NRF Centre of Excellence in Strong Materials and the University of the Witwatersrand. Anglo Platinum is acknowledged for the provision of Ru powder.

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  1. School of Chemical and Metallurgical Engineering and DST-NRF Centre of Excellence in Strong Materials, University of the Witwatersrand, Johannesburg, Private Bag 3, Johannesburg, 2050, South Africa

    Ndivhuwo B. Nelwalani & Josias W. van der Merwe

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  1. Ndivhuwo B. Nelwalani
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  2. Josias W. van der Merwe
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Correspondence to Josias W. van der Merwe.

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Nelwalani, N.B., van der Merwe, J.W. The Effect of pH on Slurry Erosion–Corrosion of Tungsten Carbide Overlays Alloyed with Ru. J Therm Spray Tech 27, 483–499 (2018). https://doi.org/10.1007/s11666-017-0676-9

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  • DOI: https://doi.org/10.1007/s11666-017-0676-9

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