Vacuum rapid fabrication of (Nb,Ti,Cr)Si2 coatings with Mo, W addition: Microstructure and oxidation resistance at 1450 °C

Abstract In order to develop the oxidation-resistant coatings for Nb based alloy at high temperatures, multi-component silicide coatings, Si-Cr-Ti coatings with and without Mo or W addition, were fabricated by spark plasma sintering process. The sintered Si-Cr-Ti coating mainly consists of single NbSi2 phase with solid solution of Ti and Cr (i.e. (Nb,Ti,Cr)Si2), while MoSi2 or WSi2 are also found in the coatings with addition of Mo or W respectively. The oxidation resistance of the coatings was tested in air at 1450 °C for 24 h. The (Nb,Ti,Cr)Si2 coating shows insufficient protection and the formed complex oxides scale turns to powders. With adding Mo or W in the coatings, dense oxide scales are formed, and the W-added coating exhibits better oxidation resistance due to the formation of a more continuous and thinner SiO2 layer.