Enhanced sulphidation/oxidation resistance of Ti–45 A l–8 N b alloy by nanostructured Cr A l YN / C r N coatings at 750 °C

This paper discusses the sulphidation/oxidation protection offered by multilayer CrAlYN/CrN coatings etched by Cr, CrAl and Y ions, deposited by a combined high power impulse magnetron sputtering (HIPIMS)/unbalanced magnetron sputtering (UBM) technique on a Ti–45Al–8Nb alloy (at%). The test was performed at 750 °C in an environment of H 2 /H 2 S/H 2 O yielding low oxygen (10 −18  Pa) and high sulphur (10 −1  Pa) partial pressures for up to 1000 h. The results show that all the exposed materials underwent uneven degradation; some places developed a thin protective oxide scale (Al,Cr) 2 O 3 with a tiny sulphur content, whilst others developed a porous non‐protective TiO 2  + Al 2 O 3 scale as well with a tiny sulphur content.