Abstract
Large-scale fabrication of MAX phase coatings such as Cr2AlC and Ti2AlC by plasma spraying is extremely challenging, owing to the ultra-high temperature and insufficient reaction time. In this research, the Cr2AlC coatings were produced by plasma spraying from Cr3C2@Al-Cr agglomerates. The influence of Al contents on microstructure and mechanics properties of coatings were investigated. Results showed the as-deposited coatings displayed a typical layered structure, mainly composed of Cr2AlC, Cr7C3, Cr23C6 and sub-stable (Cr, Al)Cx. Rapid deposition resulted in an imperfect reaction of raw powders, thus generated sub-stable (Cr, Al)Cx. The adequate Al and nonstoichiometric carbides CrCx were the main key to promote the presence of MAX-Cr2AlC phase. Nevertheless, excessive Al would create extra (Cr, Al)Cx, thus reduce the Cr2AlC content. Notably, the coatings retained high hardness (>10 GPa) and good fracture toughness (~2.5 MPa·m1/2). The micro-lamellar structure, nano-layered Cr2AlC and microcrack-toughening ensured the good mechanical properties of coatings.
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