Corrosion properties of amorphous, partially, and fully crystallized Fe68Cr8Mo4Nb4B16 alloy

• Published in: Journal of alloys and compounds 2020-06, Vol.826, p.154123, Article 154123
• Main Authors: Coimbrão, D.D., Zepon, G., Koga, G.Y., Godoy Pérez, D.A., Paes de Almeida, F.H., Roche, V., Lepretre, J.-C., Jorge, A.M., Kiminami, C.S., Bolfarini, C., Inoue, A., Botta, W.J.
• Format: Article
• Language: English
• Subjects: Alloying elements; Alloys; Amorphous alloys; Chemical Sciences; Chromium; Corrosion resistance; Corrosion resistant alloys; Crystal structure; Crystallinity; Crystallization; Crystallization nanostructure; Engineering Sciences; Fe-based amorphous alloy; Heat treatment; Homogeneous structure; Ingot casting; Material chemistry; Materials; Melt spinning; Metal surfaces; Metallic glasses; Percolation; Pitting (corrosion); Protective coatings; Ribbons; Tapes (metallic)
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2020.154123

In this work, the corrosion behavior of amorphous and partially crystallized Fe68Cr8Mo4Nb4B16 alloys has been studied. Fully amorphous ribbons were prepared by melt spinning and then partially and fully crystallized at different heat treatment temperatures. The corrosion behavior was evaluated in chloride-rich media at different pHs, ranging from acidic to alkaline. An exceptionally high corrosion resistance was observed for the new Fe68Cr8Mo4Nb4B16 amorphous alloy in the proposed media and pHs. The amorphous phase containing corrosion-resistant alloying elements such as chromium and molybdenum led to the formation of a highly stable passivating film, which coated and protected the active exposed metal surface. Partially crystallized samples heated up to 700 °C still grant the formation of a corrosion-resistant passivating layer. The presence of such a layer was correlated to the non-percolation of crystals embedded into the corrosion-resistant amorphous matrix. The corrosion resistance of fully crystalline annealed ribbons and as-cast ingots did not present the similar superior corrosion performance. This behavior was assigned to element partitioning throughout the crystallization, particularly chromium, which led to a non-homogeneous structure that preferentially triggered and held pitting corrosion along with the percolated crystalline material. These results indicate that the Fe68Cr8Mo4Nb4B16 alloy is a candidate for corrosion resistant coating where the suppression of crystallization is unavoidable. [Display omitted] •A novel Fe68Cr8Mo4Nb4B16 amorphous alloy is proposed.•The structure of the alloy annealed at different temperatures were characterized.•The amorphous alloy has excellent corrosion resistance in Cl-rich media.•Partially crystallized samples still present high corrosion resistance.•This alloy can be annealed up to 700 °C maintaining its high corrosion properties.