Comparative study of microstructural evolution during consolidation of tungsten with ceria and hafnia additions
Journal
P/M in Aerospace, Defense and Demanding Applications - 1993
Pages
111-120
ISBN
1878954318
Date Issued
1993
Author(s)
Abstract
The present paper describes the effects of ceria and hafnia additions on the microstructural evolution during consolidation of W. The consolidation of W powder during pressing and sintering was found to be modified by ceria and hafnia additions. While ceria increased the compact pressed density slightly, hafnia reduced the same. Dilatometry was used to determine densification kinetics during sintering. The activation energy for densification rate in ceria-containing W was 370±15 KJ/mole, suggesting a grain boundary diffusion controlled mechanism. However, a single mechanism could not be derived for hafnia-containing W. Scanning electron microscopy was used to study the microstructure of ingots sintered between 1000 °C and 2300 °C. In ingots sintered to more than 95% theoretical density, hafnia-containing W had a finer W grain size as well as a finer dispersion than ceria-containing W. Auger electron spectroscopy and x-ray photoelectron spectroscopy were used to examine the chemistry of the W-ceria and W-hafnia interfaces and establish trends in the behavior of the same as a function of sintering temperature. The relationships between W-ceria and W-hafnia interfaces and the sintering behavior are discussed.
Other Subjects
Cerium compounds;Composition effects;Consolidation;Crystal microstructure;Densification;Grain size and shape;Hafnium compounds;Interfaces (materials);Metal pressing;Reaction kinetics;Sintering;Spectroscopic analysis;Activation energy;Ceria;Grain boundary controlled diffusion;Hafnia;Tungsten powder metallurgy
Type
conference paper