Influence of Na₂SO₄ molten salts on the self-healing behavior of Ni/Al₂O₃ composites

ABSTRACT

The objective of this study is to investigate the influence of Na₂SO₄ molten salt on the self-healing behavior of Ni/Al₂O₃ for its utilization as the middle pressure ceramic turbine blades of aircraft. Dense 5 vol% Ni/Al₂O₃ was prepared and cracks were introduced by the Vickers indentations. The samples were heat-treated ranging from 1000°C to 1150°C for 0.5 h to 48 h in air with Na₂SO₄ molten salt. The crack lengths of samples before/after the heat treatment were measured using scanning electron microscope (SEM) and the crack disappearance rate was calculated. X-ray diffraction (XRD) results show same peaks in the samples heat-treated with and without Na₂SO₄ molten salt. The crack disappearance rate of sample heat-treated with Na₂SO₄ molten salt is higher than that without molten salt and increases according to the parabolic manner. The apparent activation energies for crack disappearance are 354 kJ/mol for the sample heat-treated with Na₂SO₄ molten salt and 390 kJ/mol for that without Na₂SO₄ molten salt. The bending strength of the sample heat-treated with Na₂SO₄ molten salt is equivalent to that of the original sample. Ni/Al₂O₃ composite exhibits excellent corrosion resistance and self-healing function even in coexistence with Na₂SO₄ molten salt.

KEYWORDS:

• Na₂SO₄ molten salt
• high-temperature corrosion
• self-healing materials
• Ni/Al₂O₃ composite
• bending strength

Disclosure statement

No potential conflict of interest was reported by the author(s).