Oxidation-resistant CoCrAl coatings fabricated by electrodeposition in combination with electrophoretic deposition

Abstract

CoCrAl coatings are one type of overlay MCrAl coatings (M = Ni, Co, Fe or their combinations), which are normally fabricated by technologies of thermal spray and physical vapor deposition. In the work, CoCrAl coatings have been fabricated by a two-step method, which integrates electrophoretic deposition (EPD) and eletrodeposition (ED). The result shows that a pre-EPDed coating on a pure cobalt substrate consisting of CrAl and Cr nanoparticles mixture can be further EDed with Co from the EPD coating/cobalt substrate interface, forming a novel type CoCrAl nanocomposite coating. Oxidation of Co9Cr6Al and Co12Cr12Al coatings (by weight percentage) in air at 900 °C indicates that both coatings are alumina formers but the coating with higher nanoparticle content forms the continuous alumina layer in a shorter time, leading to a lower oxidation rate.