A comparative study of two kinds of Y and Al modified silicide coatings on an Nb–Ti–Si based alloy prepared by pack cementation technique

Two kinds of Y and Al modified silicide coatings on an Nb–Ti–Si based alloy were prepared by pack cementation technique. The microstructure and oxidation behavior of both coatings were studied. Both coatings had a multiple layer structure, but the outer layers were composed of either Y- and Al-doped (Nb,X)Si2 or Y-doped (Nb,X)3Si5Al2 + (Nb,X)Si2 phases, respectively. The former coating could protect the substrate alloy from oxidation at 1250 °C for 100 h, but the latter coating could only endure for less than 20 h. The scale formation mechanisms and microstructural changes of both coatings upon oxidation have been illustrated.

► Two kinds of Y and Al modified silicide coatings were prepared by pack cementation.
► Y- and Al-doped (Nb,X)Si2 containing outer layer was formed in one coating.
► Y-doped (Nb,X)3Si5Al2 containing outer layer was formed in another coating.
► Oxidation behavior and failure mechanism of both coatings were investigated.