Abstract
There is an urgent need to improve the corrosion resistance of WC-based cermet coatings in different corrosive environments. The main objective of this work was to investigate the microstructure and evaluate the corrosion resistance in neutral, acidic, and alkaline electrolytes of the WC-based cermet/Fe-based amorphous alloy composite coating. Thus, a composite coating of WC–CoCr/Fe-based amorphous alloy and a single WC–CoCr coating were fabricated using the high-velocity oxygen fuel (HVOF) process. The phase composition, microstructure of the original powders, and as-sprayed coatings were studied. The detailed interface information between different compositions of the composite coating was observed by high-resolution transmission electron microscopy (HRTEM). The corrosion resistance of the coatings was studied comparatively by electrochemical tests in 3.5 wt % NaCl, 1 M HCl and 1 M NaOH solutions, respectively. Results showed that the composited coating had a dense layered structure with a composition of WC, Fe-based amorphous alloy, and small amount of W2C. It was revealed that obvious inter-diffusion exists between the interfaces of tungsten carbide/Co, Cr binder and WC–CoCr/Fe-based amorphous alloy. The electrochemical test results showed that the composite coating displayed better corrosion resistance than single WC–CoCr coating both in 3.5 wt % NaCl solution and in 1 M NaOH solution.
Highlights
As a replacement of hard chrome plating, thermal-sprayed WC-based cermet coatings have been widely used in several industries, such as aerospace, automobile, and energy, due to their excellent performance of wear resistance [1,2,3]
As the WC-based cermet coatings have been widely used, it is realized that the corrosion resistance becomes increasingly important besides wear resistance because the potential service environments for these WC-based cermet coated components are inherently corrosive in nature
Hong et al [10] prepared nanostructured WC–10Co–4Cr coating by adjusting high-velocity oxygen fuel (HVOF) process, and the coating exhibited better corrosion resistance in 3.5% NaCl solution
Summary
As a replacement of hard chrome plating, thermal-sprayed WC-based cermet coatings have been widely used in several industries, such as aerospace, automobile, and energy, due to their excellent performance of wear resistance [1,2,3]. Coatings 2018, 8, 393 resistance of WC-based cermet coatings is not so desirable [8]. Optimization of processing parameters and incorporating anti-corrosive materials have been tried to improve the corrosion resistance. References [8,9] reported that minimization or partial elimination of intrinsic defects, such as porosities, microcracks and oxide phase by optimization of processing parameters, helped to improve the corrosion resistance. Hong et al [10] prepared nanostructured WC–10Co–4Cr coating by adjusting HVOF process, and the coating exhibited better corrosion resistance in 3.5% NaCl solution. Investigation by Basak et al [11] showed nanostructured WC–Co coatings
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