Effect of thermal cycling on protective properties of alumina scale grown on thin Haynes 214 foil

• Published in: Corrosion science Vol. 98; pp. 688 - 698
• Main Authors: Chyrkin, A., Mortazavi, N., Halvarsson, M., Grüner, D., Quadakkers, W.J.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.09.2015
• Subjects: A. Alloy; A. Nickel; B. STEM; B. Thermal cycling; C. High temperature corrosion; C. Oxidation; A. Nickel; C. High temperature corrosion; B. STEM; B. Thermal cycling; C. Oxidation; A. Alloy
• ISSN: 0010-938X; 1879-0496
• DOI: 10.1016/j.corsci.2015.06.020

•Cyclic and isothermal air oxidation of Ni-base alloy HR-214 for up to 720h at 1200°C.•Duplex oxide morphology: columnar alumina overlaid by complex Ni(Al,Cr)2O4 spinel.•Thermal cycling results in tensile stresses in the oxide scale and formation of vertical cracks.•Repeated healing of cracks accelerates transition to subscale chromia formation.•Outwards transport of Cr and Ni in the cracks leads to thickening of the outer spinel layer. The isothermal and cyclic oxidation of a thin alloy 214 foil (130μm thick) has been studied in air at 1200°C for up to 720h. Haynes 214 forms a duplex oxide scale consisting of pure, columnar alumina overlaid by mixed Ni(Al,Cr)2O4 spinel with minor inclusions of (Al,Cr)2O3. A transition from external alumina to chromia scaling (abbreviated as TACS) occurs at the oxide-alloy interface after the Al reservoir of the foil is exhausted due to oxidation. The tensile cracking of the oxide scale upon thermal cycling is shown to promote the early transition from protective to accelerated breakaway oxidation.