A review on metallurgical features of hot-dip aluminized steel

Abstract

Among the various surface modification processes, the hot-dip aluminizing process has increasingly evoked considerable attention. This method has proved to be commercially cost-effective and technically better than galvanizing. In contrast to hot-dip aluminized steel components, galvanized components cannot be used in service conditions at elevated temperatures. During the last few years, intensive research by researchers has yielded new insights into metallurgical aspects of aluminized coating in as-dipped and annealed condition. The present review gives a bird’s eye view of the hot-dip aluminizing process, from the early years of its inception to the current research on aspects of the aluminized coating. The progress of research on thermodynamic studies, phase equilibria, phase identification, and their crystallographic features have been traced in this attempt. This review is not restricted to briefing the research performed so far but also points out several issues of discrepancies among the results of the published literature. Special emphasis has been given to the phase development in the coating during annealing and the increasing horizon of application of hot-dip aluminizing to alloy steels in hot stamped conditions. Reference has also been made to state-of-the-art topics embracing the current research on computer simulation software and sophisticated experimental techniques. However, lower surface hardness and economy restrict the wide application of the hot-dipping process.

Formation and Evolution of Interfacial Structure in Al–Si–Mg/Stainless Steel Bimetals during Hot-Dipping Process

“…These microstructures suggest that the Al 8 Fe 2 Si phase grew from the Fe 2 Al 5 phase during solidification. The phase compositions, microstructures, and growth sequences of the IMCs formed at the interface were similar to the results obtained in previous studies of Al-Si/(Fe or steel) bimetals [4,7]. Wang et al also confirmed that the IMC layer of Al-10Si/Fe bimetals aluminized at 700 • C for up to 30 min contains Fe 2 Al 5 , Al 8 Fe 2 Si, and Al 8 Fe 2 Si 2 [12].…”

“…These microstructures suggest that the Al8Fe2Si phase grew from the phase during solidification. The phase compositions, microstructures, and grow quences of the IMCs formed at the interface were similar to the results obtained in ous studies of Al-Si/(Fe or steel) bimetals [4,7]. Wang et al also confirmed that the The metallographic specimens were taken from a cross-section 30 mm from the bottom of AC4C/STS420 bimetal and mechanically polished using standard procedures up to colloidal silica for 20 min.…”

“…Therefore, it is apparent that the significantly higher hardness of the AC4C/STS420 interface compared with the metallic materials STS420 and AC4C was due to the formation of Fe 2 Al 5 and Al 8 Fe 2 Si phases. Slightly differing from these results, the Fe 2 Al 5 phase of Al/Fe bimetals typically exhibits a microhardness value of approximately 1000 HV [7]. Troysi et al [29] have reported that the Fe 2 Al 5 phase of aluminized 1020 steel (with a Cr composition of approximately 0.03 wt.%) exhibits a hardness value of 1070 HV.…”

“…The liquid-solid composite method is often used to prepare Al/Fe bimetallic composites because of its straightforward process and versatile material choices [5]. Though it is challenging to achieve robust metallurgical bonding owing to the physicochemical differences between Al and Fe [6,7], the removal of the Fe substrate from molten Al results in a pure Al or Al alloy layer adhering to the surface of the intermetallic compound (IMC) layer that forms during the aluminizing process [8]. The adhesion between Al and Fe is influenced by the continuous distribution of this Fe-Al IMC layer [9].…”

Recent advances in mitigating fusion zone softening during laser welding of Al-Si coated 22MnB5 press-hardened steels

“…Fan et al [70] provided a detailed summary of different coatings used for HS applications, but an updated summary has recently been provided in the review by Khan et al [12]. Dey et al [71] provided a list of reasons showcasing the benefits of hot-dip aluminized coatings over other types of coatings. Overall, the use of appropriate surface coatings is crucial to mitigate surface oxidation and corrosion in TWBs and PHS components.…”