Formation and oxidation resistance of Hf and Al modified silicide coating on Nb-Si based alloy

Abstract

Codeposition of Si, Al and Hf were prepared by pack cementation at 1300°C for 10h. The results show that the coating is composed of a thick (Nb, X)Si2 outer layer, a (Ti, Nb)5Si4 middle layer and a thin discontinuous (Cr, Al)2(Nb, Ti) inner layer. The mass gain of the coating is only 4.12mg/cm2 after isothermal oxidation at 1250°C for 100h. Some "oxide pegs" form at the interface of the oxide scale and coating. The coating exhibits good cyclic oxidation resistance due to the improved adhesion between the oxide scale and coating. © 2014 Elsevier Ltd.