Characterization and Modification of Tensile Strength Property of Cold-Sprayed Pure Iron Coating with Fine Crystal Grains

The cold spray technique is expected to effectively form a metallic coating with fine crystal grains originating from the microstructure of the original powder. We previously reported that a pure iron coating with fine crystal grains can be formed by the cold spray technique by using mechanically-milled pure iron powder. In this study, the tensile strength of the pure iron coating was investigated. The as-sprayed coating showed significantly low Young's modulus, tensile strength, and ductility owing to the low cohesion strength between particles. For tensile strength improvement, the coating was subjected to spark plasma sintering (SPS) treatment. As a result, the Young's modulus was considerably improved by the SPS treatments at 740 and 786°C; moreover, the tensile strength of the SPS-treated coating was approximately four times higher than that of the bulk material. In contrast, the ductility was not improved by the SPS treatment. The low ductility was likely attributed to the presence of Fe oxides at the particleparticle interface.