Effect of thermal conductivity on micro-arc oxidation coatings

ABSTRACT

Ceramic layers were deposited on Al–xCu (x = 1, 3, and 4.5 wt-%) alloys by micro-arc oxidation (MAO) at oxidation times of 10 and 24 min. Effects of changes in electrical conductivity (EC) and thermal conductivity (TC) of the substrate on microstructure, phase composition, residual stress (RS), and thermal shock resistance (TSR) of the layers were studied. The low EC was not conducive to the formation of α-Al₂O₃ at the 10 min oxidation. The low TC contributed to the increasing coating thickness and residual compressive stress (RCS) formation. Coatings on the alloy with 1 wt-% Cu exhibited residual tensile stress (RTS). The cavity formation induced by Al₂Cu phase affected the current and RS. The results of thermal shock tests showed that the high TC and RTS in the ceramic layers impaired the TSR. The RCS together with the high TC caused the significant cohesive failure.

KEYWORDS:

• Micro-arc oxidation
• Al–Cu alloys
• Al₂Cu phase
• electrical conductivity
• thermal conductivity
• large cavity
• residual stress
• thermal shock resistance

Acknowledgements

This research was funded by the National Natural Science Foundation of China (U1708254 and 52075087). Funding for this project was also supported by the Fundamental Research Funds for the Central Universities (N2003006 and N2103003).

Disclosure statement

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

Additional information

Funding

This work was supported by the Fundamental Research Funds for the Central Universities [grant number N2103003 and N2003006]; National Natural Science Foundation of China [grant number 52075087 and U1708254].