Microstructure and wide-temperature range tribological properties of silicide coatings on high niobium TiAl alloy

In order to improve the deficient oxidation and wear resistance of TiAlNb intermetallics, a dual rare-earth modified silicide coating was prepared on a TiAlNb9 alloy using the pack cementation process. The microstructure and phase composition of the coating were analyzed and characterized, and the friction and wear behavior of the TiAlNb9 substrate and the Si-Ce-Y co-diffused coating against WC balls has been comparatively investigated across a broad temperature range. The results show that the coatings prepared with different activators, including NaF, NH₄Cl, and AlCl₃·6H₂O, have multi-layer structures: From the surface to the interior, the coatings are composed of outer layers of (Ti,Nb)Si₂, (Ti,Nb)₅Si₄ and (Ti,Nb)₅Si₃, middle layers of (Ti,Nb)₅Si₄ and (Ti,Nb)₅Si₃, and the inner layers of TiAl₂. The activators have imposed a significant impact on the density of the co-diffusion coatings. Under experimental conditions, the friction and wear resistance of the Si-Ce-Y co-diffusion coating are significantly better than those of the TiAlNb9 substrate. The wear mechanisms of the TiAlNb9 substrate at 20℃ are abrasive wear and plowing wear, while at 600℃, the main wear mechanisms are oxidational wear, plowing wear, and abrasive wear. The wear mechanisms of the Si-Ce-Y co-diffusion layer at 20℃ and 600℃ are similar, mainly including delamination wear and abrasive wear.