Formation of microstructural features in hot-dip aluminized AISI 321 stainless steel

• Published in: International journal of minerals, metallurgy and materials Vol. 25; no. 2; pp. 190 - 198
• Main Authors: Huilgol, Prashant, Rajendra Udupa, K., Udaya Bhat, K.
• Format: Journal Article
• Language: English
• Published: Beijing University of Science and Technology Beijing 01.02.2018; Springer Nature B.V; Department of Metallurgical & Materials Engineering, National Institute of Technology Karnataka, Surathkal, Mangalore-575025, India
• Subjects: Aluminides; Austenitic stainless steels; Carbon steels; Ceramics; Characterization and Evaluation of Materials; Chemistry and Materials Science; Composites; Corrosion and Coatings; Corrosion resistance; Electron microscopy; Glass; Heat resistant steels; High temperature; Hot dip aluminizing; Immersion coating; Intermetallic compounds; Intermetallic phases; Materials Science; Metallic Materials; Microscopy; Natural Materials; Oxidation resistance; Stainless steel; Substrates; Surfaces and Interfaces; Thin Films; Tribology; 微结构特征;AISI;不锈钢;扫描电子显微镜;表面涂层技术;HDA;高温度;金属间; hot-dip aluminizing; stainless steel; intermetallic phases; microstructural features; aluminide layer
• ISSN: 1674-4799; 1869-103X
• DOI: 10.1007/s12613-018-1562-2

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 Al_7Cr and Al_3Fe dispersed in an Al matrix. Twinning was observed in both the Al_7Cr and the Al_3Fe phases. Furthermore, the aluminide layer comprised a mixture of nanocrystalline Fe_2Al_5, Al_7Cr, and Al. Details of the microstructural features are presented, and their formation mechanisms are discussed.