Anodic plasma electrolytic deposition of composite coating on ferrous alloys with low thermal conductivity and high adhesion strength

Chen Zhao, Jiayi Sun, Xueyuan Nie*, Jimi Tjong, D.T.A. Matthews*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

This work reports the preparation of ceramic coatings as potential thermal barrier coatings (TBC) on ferrous alloys, targeting automotive applications. The coatings are shown to have excellent adhesion due to fabrication by plasma electrolytic aluminating (PEA), an anodic plasma electrolytic deposition process. The PEA process was conducted in an aluminate-containing aqueous electrolyte under a high voltage. The coating has superior adhesion (>60 MPa) and low thermal conductivity (~0.5 W/mK) measured by the adhesive tensile test and steady-state heat flow methods, respectively. Scanning electron microscope (SEM) observations reveal that the coatings have numerous mesopores. X-ray diffraction (XRD) analysis shows that the coating mainly consists of α-Al2O3 and hercynite (FeAl2O4) with (ultra-)fine grain size. Amorphous phases are also identified in the coatings. These mesopores, fine grain size and amorphous phases contributed to the low thermal conductivity of the coating. The hercynite phase indicated that the substrate was involved in the PEA reaction and thus the coating had a metallurgical bonding to the substrate. After cyclic thermal shock tests (quenching from 425 °C to 20 °C in water 100 times), the coating retained its porous structure without spallation. The results demonstrate that the ceramic composite coating may be a good candidate for thermal management of automotive engines.
Original languageEnglish
Article number126081
Number of pages35
JournalSurface and coatings technology
Volume398
Early online date19 Jun 2020
DOIs
Publication statusE-pub ahead of print/First online - 19 Jun 2020

Keywords

  • UT-Hybrid-D
  • Plasma electrolytic aluminating
  • Thermal conductivities
  • Thermal stability
  • Adhesive strength
  • Composite coating

Fingerprint Dive into the research topics of 'Anodic plasma electrolytic deposition of composite coating on ferrous alloys with low thermal conductivity and high adhesion strength'. Together they form a unique fingerprint.

  • Cite this