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Cold-Sprayed AZ91D Coating and SiC/AZ91D Composite Coatings

College of Chemistry and Chemical Engineering, Southwest Petroleum University, Chengdu 610500, China
Université de Lyon, INSA de Lyon, MATEIS CNRS UMR 5510, 69621 Villeurbanne, France
Key Laboratory of Marine Materials and Related Technologies, Key Laboratory of Marine Materials and Protective Technologies of Zhejiang Province, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, China
ICB UMR 6303, CNRS, University Bourgogne Franche-Comté, UTBM, 90100 Belfort CEDEX, France
Authors to whom correspondence should be addressed.
Coatings 2018, 8(4), 122;
Received: 21 January 2018 / Revised: 23 March 2018 / Accepted: 23 March 2018 / Published: 26 March 2018
(This article belongs to the Special Issue New Generation Coatings for Metals)
As an emerging coating building technique, cold spraying has many advantages to elaborate Mg alloy workpieces. In this study, AZ91D coatings and AZ91D-based composite coatings were deposited using cold spraying. Coatings were prepared using different gas temperatures to obtain the available main gas temperature. Compressed air was used as the accelerating gas, and although magnesium alloy is oxidation-sensitive, AZ91D coatings with good performance were obtained. The results show that dense coatings can be fabricated until the gas temperature is higher than 500 °C. The deposition efficiency increases greatly with the gas temperature, but it is lower than 10% for all coating specimens. To analyze the effects of compressed air on AZ91D powder particles and the effects of gas temperature on coatings, the phase composition, porosity, cross-sectional microstructure, and microhardness of coatings were characterized. X-ray diffraction and oxygen content analysis clarified that no phase transformation or oxidation occurred on AZ91D powder particles during cold spraying processes with compressed air. The porosity of AZ91D coatings remained between 3.6% and 3.9%. Impact melting was found on deformed AZ91D particles when the gas temperature increased to 550 °C. As-sprayed coatings exhibit much higher microhardness than as-casted bulk magnesium, demonstrating the dense structure of cold-sprayed coatings. To study the effects of ceramic particles on cold-sprayed AZ91D coatings, 15 vol % SiC powder particles were added into the feedstock powder. Lower SiC content in the coating than in the feedstock powder means that the deposition efficiency of the SiC powder particles is lower than the deposition efficiency of AZ91D particles. The addition of SiC particles reduces the porosity and increases the microhardness of cold-sprayed AZ91D coatings. The corrosion behavior of AZ91D coating and SiC reinforced AZ91D composite coating were examined. The SiC-reinforced AZ91D composite coating reveals higher corrosion potential than magnesium substrate; therefore, it serves as a cathode for the magnesium substrate, the same as the AZ91D coating on magnesium substrate. As the SiC powder is semi-conductive, the embedded SiC particles reduce the electrochemical reaction of the AZ91D coating. The addition of SiC particles increases the corrosion potential of the coating, meanwhile increasing the galvanic potential and decreasing the negative galvanic current of the coating-substrate couple. View Full-Text
Keywords: cold spraying; coating; magnesium alloy; composite coatings; corrosion; microstructure cold spraying; coating; magnesium alloy; composite coatings; corrosion; microstructure
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MDPI and ACS Style

Wang, Y.; Normand, B.; Suo, X.; Planche, M.-P.; Liao, H.; Tang, J. Cold-Sprayed AZ91D Coating and SiC/AZ91D Composite Coatings. Coatings 2018, 8, 122.

AMA Style

Wang Y, Normand B, Suo X, Planche M-P, Liao H, Tang J. Cold-Sprayed AZ91D Coating and SiC/AZ91D Composite Coatings. Coatings. 2018; 8(4):122.

Chicago/Turabian Style

Wang, Yingying, Bernard Normand, Xinkun Suo, Marie-Pierre Planche, Hanlin Liao, and Junlei Tang. 2018. "Cold-Sprayed AZ91D Coating and SiC/AZ91D Composite Coatings" Coatings 8, no. 4: 122.

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