High-temperature wettability and interactions between Hf-containing NbSi-based alloys and Y2O3 ceramics with various microstructures

Publication date: 15 January 2018
Source:Materials & Design, Volume 138
Author(s): Beibei Wan, Huarui Zhang, Ming Gao, Peng Bai, Hu Zhang
To obtain improved mould shells with appropriate microstructures for directional solidification casting of NbSi-based alloys, Y2O3 ceramics with various microstructures were designed and characterized. The mechanisms of high-temperature wettability and interactions between NbSi-based alloys and Y2O3 ceramics were studied. The results showed that there was a characteristic transition in the wettability between the molten alloys and ceramics when the Y2O3 microstructure changed. The spreading rate gradually decreased and the apparent equilibrium contact angle changed from 70.2° to 112.6° with the level of open porosity of Y2O3 ceramics increasing from 3.6% to 27.2%. Wetting kinetics analyses indicated that the movement of the triple line during the wetting process was driven by the formation of continuous HfO2 reaction layer in the alloy-ceramic interface. The content of HfO2 particles inner the alloy matrix with the level of open porosity of Y2O3 ceramics increasing from 3.6% to 27.2% initially gradually decreased and subsequently increased. Y2O3 with open porosity level of about 20.7% were the most beneficial for directional solidification casting of high-purity Hf-containing NbSi-based alloys.

Graphical abstract

http://ift.tt/2lXyWFW