Characterization of Coatings on Grey Cast Iron Fabricated by Hot-dipping in Pure Al, AlSi11 and AlTi5 Alloys

Open access

Abstract

Flake graphite cast iron was hot-dip coated with pure aluminium or aluminium alloys (AlSi11 and AlTi5). The study aimed at determining the influence of bath composition on the thickness, microstructure and phase composition of the coatings. The analysis was conducted by means of an optical microscope and a scanning electron microscope with an EDS spectrometer. It was found that the overall thickness of a coating was greatly dependent on the chemical composition of a bath. The coatings consisted of an outer layer and an inner intermetallic layer, the latter with two zones and dispersed graphite. In all the cases considered, the zone in the inner intermetallic layer adjacent to the cast iron substrate contained the Al5Fe2 phase with small amount of silicon; the interface between this phase and the cast iron substrate differed substantially, depending on the bath composition. In the coatings produced by hot-dipping in pure aluminium the zone adjacent to the outer layer had a composition similar to that produced from an AlTi5 bath, the Al3Fe phase was identified in this zone. The Al3Fe also contained silicon but its amount was lower than that in the Al5Fe2. In the coatings produced by hot-dipping in AlSi11, the zone adjacent to the outer layer contained the Al3FeSi phase. The analysis results showed that when AlSi11 alloy was applied, the growth mode of the inner layer changed from inwards to outwards. The interface between the Al5Fe2 phase and the cast iron substrate was flat and the zone of this phase was very thin. Locally, there were deep penetrations of the Al5FeSi phase into the outer layer, and the interface between this phase and the outer layer was irregular. Immersion in an AlTi5 bath caused that the inner intermetallic layer was thicker than when pure aluminium or AlSi11 alloy baths were used; also, some porosity was observed in this layer; and finally, the interface between the inner layer and the cast iron substrate was the most irregular

[1] Cheng,W. J. & Wang, C. J. (2011). Microstructural evolution of intermetallic layer in hot-dipped aluminide mild steel with silicon addition. Surf. Coat. Technol. 205, 4726-4731. DOI: 10.10.16/j.surfcoat.2011.04.061.

[2] Pietrowski, S. & Szymczak, T. (2011). Theoretical basis of Al-Si coat crystallization on gray and nodular cast iron and making the layered items using it. Journal of Achievements in Materials and Manufacturing Engineering. 49(2), 421-439.

[3] Pietrowski, S. & Szymczak, T. (2006). The influence of selected technological elements on the structure of alphinizing coat on iron alloys. Archives of Foundry. 6(19), 251-266.

[4] Gembalski, S. (1969). Diffusion aluminizing of steel, cast iron, copper and titanium. Metal Science and Heat Treatment. 9(9), 646-651.

[5] Gierek, A. & Bajka, L. (1976). Dip aluminized - properties and applications. Design Issues. 12, 356-360.

[6] Springer, H., Kostka, A., Payton, E. J., Raabe, D., Kaysser- Pyzalla, A. & Eggeler, G. (2011). On the formation and growth of intermetallic phases during interdiffusion between low-carbon steel and aluminium alloys. Acta Mater. 59, 1586-1600. DOI: 10.1016/j.actamat.2010.11.023.

[7] Maitra, T. & Gupta, S. P. (2003). Intermetallic compound formation in Fe-Al-Si ternary system: Part II Mater. Charact. 49, 293-311. DOI: 10.1016/S1044-5803(03)00005-6.

[8] Lin, M. B., Wang, C. J. & Volinsky, A. A. (2011). Isothermal and thermal cycling oxidation of hot-dip aluminide coating on flake/spheroidal graphite cast iron.Surf. Coat. Technol. 206, 1595-1599. DOI: 10.1016/j. surfcoat.2011.06.010

Archives of Foundry Engineering

The Journal of Polish Academy of Sciences

Journal Information


CiteScore 2016: 0.42

SCImago Journal Rank (SJR) 2016: 0.192
Source Normalized Impact per Paper (SNIP) 2016: 0.316

Metrics

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 162 162 11
PDF Downloads 70 70 4