Influence of the dew point of the atmosphere on the sintering of doped molybdenum

While sintering Mo-0,3 % La2O3 in hydrogen, the content of water vapor in the atmosphere increases due to the dehydration of La(OH)3 to La2O3, on the one hand, and the removal of residual oxygen in the powder, on the other hand. This water vapor cannot be removed sufficiently from the center of larger ingots and a dew point gradient is formed. A description of experimental observations of the effect of the dew point of the sintering atmosphere on densification, and the evolution of porosity and microstructure is given. A shift in the onset of densification towards higher temperatures with increasing dew point was observed. The density of specimens sintered in atmospheres with a high dew point lags behind the values, obtained in dry hydrogen. (author)