Development and characterization of an iron aluminide coating on mild steel substrate obtained by friction surfacing and
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ORIGINAL ARTICLE
Development and characterization of an iron aluminide coating on mild steel substrate obtained by friction surfacing and heat treatment Fernanda D. Troysi 1
&
Pedro P. Brito 1
Received: 26 May 2020 / Accepted: 22 October 2020 # Springer-Verlag London Ltd., part of Springer Nature 2020
Abstract Iron aluminides are intermetallic Fe–Al alloys known for their high temperature corrosion and oxidation resistance, which makes them candidate materials for high temperature applications. In the present work, the formation of an iron aluminide layer on a mild steel substrate by friction stir surfacing of aluminium alloy AA6351 followed by isothermal heat treatment is reported. After Al-alloy deposition, the samples were subjected to annealing at temperature of 500, 550, 600 and 650 °C for various times up to 120 h. Microstructure analyses conducted by XRD and SEM/EDS indicated the formation of a homogenous layer of Fe2Al5 with average hardness value of 1070 HV for a 72-h treatment at 650 °C. The electrochemical corrosion behaviour of the developed coatings was analysed, and it was possible to show that friction stir surfacing followed by heat treatment constitutes an effective processing route for obtaining iron aluminide coatings on conventional steel substrates. Keywords Friction stir surfacing . Iron aluminide . Diffusion . Coating . Corrosion
1 Introduction Iron aluminides are Fe–Al intermetallic alloys considered candidate materials for high temperature applications because of their low cost, elevated strength to weight ratio and high resistance to corrosion and oxidation in high-temperature environments [1–4]. These materials have been investigated as structural components for heat exchangers operating with liquid metals, found in nuclear power and concentrated solar power facilities [5, 6], high temperature KCl environments found in biomass plants [7, 8], among others. In addition, iron aluminides stand out regarding the potential for reducing structural weight in comparison to conventional stainless steels (up to ~ 25%) because of the elevated aluminium content [9]. In part, however, the widespread use of iron aluminides is currently hindered by poor room temperature ductility, which limits processing options, excluding forming operations such
* Fernanda D. Troysi [email protected] 1
Pontifical Catholic University of Minas Gerais (PUC Minas), Av. Dom José Gaspar 500, Bairro Coração Eucarístico, Belo Horizonte, Minas Gerais 30535-901, Brazil
as drawing or rolling. As an alternative, the development of iron aluminide coatings on conventional steel substrates has been sought recently, mainly by thermal spraying or by aluminizing followed by diffusion annealing treatments. Recently, the development of iron aluminide coatings by arc-welding processes has also been analysed [10, 11]. In spite of positive results, thermal spray coatings are highly sensitive to the deposition parameters and are known to exhibit pores [12–16], chemical composition heterogeneity [17] and oxide inclusions [16
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