Relationship between the B4C reinforcement content and the properties of MAO films on the B4C/Al matrix composites

Abstract Thermal control coating is necessary for the B 4 C/Al matrix composites (AMCs) used in nuclear power field. Micro-arc Oxidation (MAO) technology is a suitable method to prepare thermal control coating on B 4 C/AMCs, but the B 4 C reinforcements has a great influence on the MAO process. In this paper, the effects of the B 4 C content on the spark discharge, microstructure and properties of the MAO films were studied by a Dual-channel Oscilloscope, Scanning Electron Microscopy (SEM) and Electrochemical Impedance Spectroscopy (EIS). The results indicate that the spark discharge in the early stage of oxidation is inhibited with the increase of the B 4 C particles in AMCs, but the effect declines in the later stage. Also, the compactness and blackness of the MAO films reduce due to the negative effect of the B 4 C particles on the oxidation process, but the lowest emissivity of the MAO film is still higher than 0.85, which can still meet the general requirement for thermal control coatings in actual applications.