New method of in-situ fabrication of protective coatings based on Fe–Al intermetallic compounds

Abstract

The paper presents the initial investigation results on producing surface protective coatings made of Fe–Al intermetallic compounds on steel substrates. The Fe–Al coating is obtained in a two-step process. First, the steel substrate is thermally sprayed with pure aluminium having a thickness of about 0.3° mm. In this way both components (Fe, Al) are prepared for subsequent melting and synthesis. In the final step, the aluminium coating is remelted together with the surface of the steel substrate by the CO2 laser beam. The resulting molten pool consists of aluminium and iron in equal parts, allowing it to form a Fe–Al intermetallic compound during the in-situ process of remelting. The formation of Fe–Al intermetallic compound has been verified by the microhardness and X-ray diffraction measurements of the analysed coatings. The developed method is a cheap alternative compared with other surface modification processes utilizing commercially prepared intermetallic coating materials. In addition, the remelting process substantially increases the strength of the coating bond, which has a magnitude close to that observed for hard-facing processes.