Cyclic oxidation of slurry silicide-aluminide coatings formed on Ti-6Al-4V alloy

ABSTRACT A proprietary slurry cementation method was used to produce silicide-aluminide coatings on alloy Ti-6Al-4V. The cementation processes were carried out at 900–1100 °C for 2–6 h. The coatings exhibited a stratified configuration characterised by a phase arrangement that demonstrates favourable attributes pertaining to mechanical and corrosion resistance capabilities, namely, the presence of aluminium-enriched phases at the coating surface and titanium-enriched phases proximity to the substrate. The cyclic oxidation behaviour at 800 °C for 30 twenty-two-hour cycles was investigated. The characterisation of the structure of coatings was carried out through the use of scanning microscopy, X-ray microanalysis, and X-ray diffraction techniques. The coatings have excellent resistance to cyclic oxidation, resulting from the gradient structure and the establishment of a protective alumina layer on the surface. The coatings were characterised by good resistance to thermal shocks. The microcracks formed during thermal shocks were filled with an alumina, which renders the coatings self-healing.