In-situ synthesis of Y2W3O12 within a Co-based superalloy powder mixture

Abstract

In-situ synthesis of Y 2 W 3 O 12 within a Co-based superalloy powder mixture In this work, the synthesis of the negative thermal expansion ceramic Y 2 W 3 O 12 within a Co-based superalloy was analyzed in detail. On the basis of thermal analysis of the synthesis from the feedstock powders Y 2 O 3 and WO 3 further experiments were conducted. Thermal behavior and stability of different mixtures of the powders Y 2 O 3 , WO 3 and the Co-based superalloy were investigated. The qualitative and quantitative results of the synthesis separately and within the superalloy are presented as achieved by energy dispersive X-ray analysis, X-ray powder diffraction, differential thermal analysis and thermal gravimetric analysis. It was found that the synthesis of yttrium tungstate inside the Co-based superalloy is possible with a defined temperature program and a simple basic production process of powder mixtures.

Self-organized nanostructuring of composite coatings at high temperatures for drag reduction and self-cleaning

“…The phase transformation is apparent. In the figure, the peaks of Y 2 O 3 and the WO 3 are not marked for clarity, but they fully disappeared after the DTA reaction [8].…”

“…The onset-temperature of the first reaction is 361°C. The second reaction started at 743°C, which can be attributed to phase transformations [8]. After the DTA measurement, the powder changed color from yellow into white.…”

“…In this temperature range, only one ceramic can be used. Y 2 W 3 O 12 is stable above 1050°C (up to 1373°C, [8,9]) and forms out of a stoichiometric mixture of Y 2 O 3 and WO 3 by annealing at or above 1163°C [8]. Y 2 W 3 O 12 is a highly hygroscopic material, so it needs to be produced in-situ inside the protecting MCrAlY-matrix [9,10].…”