Structure and High-Temperature Oxidation Performance of Si-Co Diffusion Coatings Prepared on a TiAl-Nb Alloy

Si-Co diffusion coatings were prepared on a Y-modified TiAl-Nb alloy using the pack cementation process. The structures of at different temperatures (1050, 1080, and 1120 °C) Co contents (5, 10, 20 wt.%) comparatively studied. possessed typical structure (Ti,X)Si2+Ti5Si4 (X represents Nb Al elements) outer layer with Co-rich superficial zone, Ti5Si4+Ti5Si3 middle layer, TiAl2 inner layer. Increasing co-deposition temperature in range 1050–1120 °C led to larger coating thickness but more-porous structure, while increasing 5–20 wt.% caused lower growth rate. formation followed an orderly process depositing Si first then Co. had much better anti-oxidation performance than both substrate pure silicide coating. After undergoing oxidation 1000 for 100 h, parabolic rate was approximately 6.16 × 10−3 mg2/cm4h1, which those by about two orders magnitude one order magnitude.