| YAN Xi-feng,WANG Hai-bin,QIU Qing-fan,SONG Xiao-yan.Corrosion Behavior and Corrosion Resistance Mechanism of HVOF Sprayed WC-WCoB Coating in Molten Zinc[J],48(4):48-54 |
| Corrosion Behavior and Corrosion Resistance Mechanism of HVOF Sprayed WC-WCoB Coating in Molten Zinc |
| Received:November 14, 2018 Revised:April 20, 2019 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2019.04.007 |
| KeyWord:WCoB η phase WC-based coating oxidation resistance microcrack corrosion resistance to molten zinc |
| Author | Institution |
| YAN Xi-feng |
Key Laboratory of Advanced Functional Materials under the Ministry of Education of China, School of Materials Science and Engineering, Beijing University of Technology, Beijing , China |
| WANG Hai-bin |
Key Laboratory of Advanced Functional Materials under the Ministry of Education of China, School of Materials Science and Engineering, Beijing University of Technology, Beijing , China |
| QIU Qing-fan |
Key Laboratory of Advanced Functional Materials under the Ministry of Education of China, School of Materials Science and Engineering, Beijing University of Technology, Beijing , China |
| SONG Xiao-yan |
Key Laboratory of Advanced Functional Materials under the Ministry of Education of China, School of Materials Science and Engineering, Beijing University of Technology, Beijing , China |
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| Abstract: |
| The work aims to reveal the corrosion behavior and mechanisms of newly developed WC-WCoB coating against molten zinc so as to improve the corrosion resistance of WC-based coatings. WC-WCoB thermal spray feedstock powder with a high sphericity and high density was prepared by the centrifugal spray drying and subsequent vacuum heat-treatment with WC, Co and WB as raw materials. The coating was then fabricated by the high velocity oxy-fuel (HVOF) spraying technique. The cross-sectional microstructures of the coating after immersion in the liquid zinc for various periods were observed to evaluate the corrosion resistance. The composition, structure and oxidation resistance of the coatings were characterized by X-ray diffraction, thermogravimetric/differential thermal analysis, scanning electron microscopy and energy spectrum analysis. WCoB phase had no chemical reaction with the molten zinc. Besides, there was no evidence showing the diffusion of Zn into the prepared WC-WCoB coating even when the coating had been immersed into the liquid zinc for 600 h. However, the microcracks were easy to initiate at the outer surface of the coating due to the slow oxidation of oxygen dissolved in the liquid zinc. The cracks gradually propagated towards the inner and eventually led to the exfoliation of coating materials layer by layer. After the immersion in molten zinc for 600 h, the area without corrosion accounted for 56.3% of the total area of the WC-WCoB coating. The addition of a certain amount of WB to the conventional WC-Co coating can cause the entire transformation of Co into the WCoB phase. As compared to the currently widely used WC-η coating, the developed WC-WCoB coating in the present work exhibits much higher oxidation resistance. As a result, the formation and growth rates of the oxidation-induced cracks in WC-WCoB coating can be significantly decreased, which then contributes to better corrosion resistance to molten zinc at the macro level. |
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