Co-deposition of Si and B to form oxidation-resistant coatings on an Nb-Ti-Si based ultrahigh temperature alloy by pack cementation technique

In this work, we study the oxidation behavior of a B-modified silicide coating at 900-1350°C. The coating was prepared by pack cementation, which mainly consisted of a (Nb,X)Si₂+(Nb,X)B₂ outer layer, a (Nb,X)Si₂ intermediate layer and an inner layer. At 900 and 1250°C, the evolution of the mass gain versus time showed parabolic-like kinetics; while at 1350°C, the evolution seemed to follow a linear-like kinetic, but could protect the alloy from oxidation for at least 60h. The good oxidation resistance of the B-modified silicide coating was attributed to the formation of a dense glass-like scale.