The effect of grain refinement on the oxidation and phase transformation of alumina scale on Ni2Al3 coating. (July 2022)

• Record Type: Journal Article
• Authors: Khan, A.; Ullah, Ihsan; Ullah, A.; Shah, S.S.A.; Zhang, S.H.; Song, G.S.
• Is Part Of: Intermetallics. Volume 146(2022)
• Publication Date: 2022-07
• Subjects: Ni2Al3 coating -- Grain refinement -- SEM -- TEM -- Raman spectroscopy -- Oxidation -- Alumina scale formation; Intermetallic compounds -- Metallography -- Periodicals; Metallic glasses -- Periodicals; Composés intermétalliques -- Métallographie -- Périodiques; 669.94
• DOI: 10.1016/j.intermet.2022.107571
• Languages: English
• ISSNs: 0966-9795

Abstract

Abstract: An ultrafine-grained (UFG) and coarse-grained (CG) Ni2 Al3 coating were prepared by aluminizing pure nickel substrate with and without nanocrystalline Ni film using an aluminization pack cementation process at 620 °C for 5 h. The oxidation kinetics and cyclic oxidation result show that the UFG-Ni2 Al3 coating significantly enhances the oxidation-resistant with respect to the CG-Ni2 Al3 coating in air at 900 °C. The SEM/EDS results confirmed that the microstructure of two δ-Ni2 Al3 coatings is free of pores, cracks, and voids. The UFG-Ni2 Al3 coating promotes the phase transformation with respect to the CG-Ni2 Al3 coating after oxidation for various times were investigated by using photo-stimulated luminescence spectroscopy (PSLS) analysis. The experimental result also confirmed that the UFG-Ni2 Al3 coating, on which an adherent alumina scale grew, can significantly control the formation of cavities at the scale/coating interface. Highlights: Successfully fabricated the coarse-grained (CG) and ultrafine-grained (UFG) Ni2 Al3 coatings. The grain refinement caused faster promotion of thermally grown alumina from θ-to-α phase. The grain refinement can be noticeably increased the oxidation resistance of Ni2 Al3 coatings. Ultrafine-grained Ni2 Al3 coating helped to form an adherent alumina scale.