Abstract
Several kinds of WC-reinforced coatings were prepared by high-velocity oxygen-fuel spray (HVOF) and electric contact strengthening (ECS), respectively, and their corrosion behaviors in 3.5% NaCl solution were investigated. The microstructure, element distribution, phase and corrosion resistance of these coatings were compared. The results showed that, compared with HVOF-sprayed coatings, the ECS-prepared coatings were denser and with lower porosity. Simultaneously, the ECS coatings that used raw powder commercial WC-12Co retained the original spherical geometry of the hard phase. In open-circuit potential measurements, these ECS coatings gave higher stable potentials (Eocp). In potentiodynamic polarization tests, although the corrosion currents (icorr) of the homogeneous coatings were approximately the same, these ECS coatings still exhibited higher corrosion potentials (Ecorr). The spherical geometric distribution of the hard phase led to a bounded diffusion model caused by the diffusion change of corrosion products.
Highlights
WC-reinforced coatings are widely used in mining, oil drilling and other industries due to their excellent performance [1,2]
The electrochemical impedance spectroscopy (EIS) curves in 3.5% NaCl solution were measured after all coatings had been stabilized in the Open circuit potential (OCP) test for 4 h
During the corrosion process of the WC-reinforced coating in 3.5% NaCl solution, the hard phase acted as the cathode, and the bonding phase acted as the anode in galvanic corrosion
Summary
WC-reinforced coatings are widely used in mining, oil drilling and other industries due to their excellent performance [1,2]. Commercial WC-12Co powder is widely applied by synchronous powder feeding to deposit this coating. This commercial powder was formed by the agglomeration and sintering of WC and Co. It can be observed that fine-grained WC particles are uniformly combined with Co at high magnification. It can be observed that fine-grained WC particles are uniformly combined with Co at high magnification This powder can achieve enough kinetic energy in jet flight, and coatings can be obtained with sufficiently fine particle size in the hard phase
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