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

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)Si-2), 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 degrees C for 24 h. The (Nb,Ti,Cr)Si-2 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.