Oxidation behaviour of a Ge-modified silicide coating on an Nb-Si based alloy in the moderate temperature range

摘要

The oxidation characteristics of Ge-modified silicide coating on the Nb-Si based alloy within the moderate temperatures were investigated. Results show that the mass gains of the coated alloys are 0.41, 0.58 and 0.37 mg/cm(2) after oxidation at 700 degrees C, 750 degrees C and 800 degrees C for 100 h. There is no pest phenomenon at the test temperatures. The oxide scale is composed of amorphous aluminosilica and SiO2-GeO2 with TiO2 dispersed in some of SiO2-GeO2. The good oxidation resistance of the Ge-modified silicide coating at moderate temperatures is attributed to the selective oxidation of Ti and Si, as well as the formation of glassy SiO2-GeO2.