Faculty Publications
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Item Formation of microstructural features in hot-dip aluminized AISI 321 stainless steel(University of Science and Technology Beijing, 2018) Huilgol, P.; Rajendra Udupa, K.; Udaya Bhat, K.Hot-dip aluminizing (HDA) is a proven surface coating technique for improving the oxidation and corrosion resistance of ferrous substrates. Although extensive studies on the HDA of plain carbon steels have been reported, studies on the HDA of stainless steels are limited. Because of the technological importance of stainless steels in high-temperature applications, studies of their microstructural development during HDA are needed. In the present investigation, the HDA of AISI 321 stainless steel was carried out in a pure Al bath. The microstructural features of the coating were studied using scanning electron microscopy and transmission electron microscopy. These studies revealed that the coating consists of two regions: an Al top coat and an aluminide layer at the interface between the steel and Al. The Al top coat was found to consist of intermetallic phases such as Al7Cr and Al3Fe dispersed in an Al matrix. Twinning was observed in both the Al7Cr and the Al3Fe phases. Furthermore, the aluminide layer comprised a mixture of nanocrystalline Fe2Al5, Al7Cr, and Al. Details of the microstructural features are presented, and their formation mechanisms are discussed. © 2018, University of Science and Technology Beijing and Springer-Verlag GmbH Germany, part of Springer Nature.Item Microstructure evolution in Al 6061 coating deposited on Al 2024 substrate by friction surfacing(Elsevier Ltd, 2022) Sudhish, R.; Udaya Bhat, K.In the present investigation, the microstructure evolution in Al 6061 coating deposited by friction surfacing on Al 2024 was studied in detail. The age hardening behaviour of the developed coating was also analysed. The Al 6061 tool material was solutionized prior to the coating process. The microstructural analysis revealed that, an ultra-fine grain microstructure could be achieved in coating by the coating process wherein the Al 2024 substrate has marginal modification in microstructure. Continuous dynamic recrystallization is identified as the mechanism of ultra-fine grain formation. Also, it was found that the process induced thermo-mechanical effect causing an increment in ageing kinetics. The enhanced ageing kinetics and formation of ultra- fine grains collectively improved the peak aged hardness of the friction surface coating, made using Al 6061. © 2022 Elsevier Ltd