High temperature oxidation behaviour of mono-layer and bi-layer coatings

Abstract

In the current work, the mono-layer Al-Cr-Ni coating and the bi-layer Al-Ni/Al-Cr coating were successfully synthesised on the Ti-6Al-4V alloy substrate by mechanical alloying. The effect of powder ratio was studied. The microstructure and phase composition of the two coatings were investigated. The mono-layer coating was composed of grey black composite structure. In the bi-layer coating, the Al-Cr outer layer exhibited a composite structure similar to the Al-Cr-Ni coating. The results showed the approximate thickness of Al-Cr-Ni coating was 140 μm, while that of bi-layer coating was more than 200 μm. Both coatings were well bonded to the substrate. After 850°C of cyclic oxidation for 100 h, cracks only occurred at the interface of the mono-layer coating, and no significant defects were found at the two interfaces of the bi-layer coating. The cyclic oxidation test results showed the bi-layer coatings exhibited more excellent oxidation resistance.

Critical Raw Materials Saving by Protective Coatings under Extreme Conditions: A Review of Last Trends in Alloys and Coatings for Aerospace Engine Applications

“…Cr-Al and Ni-Al coatings have been applied on TiAl alloys to increase the oxidation resistance [ 225 , 226 ]. In a very recent work by Guo et al [ 226 ], Ni-Cr-Al monolayer and Ni-Al/Cr-Al bilayer coatings were synthesized on the Ti–6Al–4V alloy, showing the occurrence of some cracking effect at the interface between the monolayer coating and the alloy surface, while no significant defects were observed in the bilayer structure, which resulted in a better oxidation resistance.…”

Corrosion resistance of modified YSZ coatings subjected to CMAS attacks

“…(3) Modifications of YSZ using doping stabilizers have included alumina, titanium dioxide and rare-earth oxides. Padture et al [17,18] first incorporated alumina and titanium dioxide in the shape of a solid solution into YSZ TBCs using SPPS processing.…”

“…(3) Modifications of YSZ using doping stabilizers have included alumina, titanium dioxide and rare-earth oxides. Padture et al [17,18] first incorporated alumina and titanium dioxide in the shape of a solid solution into YSZ TBCs using SPPS processing. The idea was to incorporate Al 3+ and Ti 4+ into the CMAS glass during TBC interactions to promote the TiO 2 -assisted crystallization of the Al 2 O 3 -enriched glass to anorthite (CaAl 2 Si 2 O 8 ).…”