Relations Between Chemistry, Solidification Behaviour, and Microstructure in IN 100
This co-operative study was aimed at assessing the influence of trace-and major alloying-elements on the solidification behaviour and as-cast microstructure of IN 100. The work was carried out on six distinct master heats selected for their particular contents in Ti, Nb, Hf, N2 and O2. All samples and test pieces were taken from actual turbine blades cast from these master heats at SNECMA and Fabrique Nationale.
The solidification behaviour was studied through differential thermal analysis (D.T.A.) which made it possible to determine the transformation temperatures extrapolated to zero cooling rate for rapid dendrite growth, carbide precipitation, eutectic formation, and secondary γ′ precipitation. The microstructure observed in a well defined zone of the blade airfoil was carefully characterized by quantitative metallography as regards eutectic and carbide distributions. In both cases, the alloy chemistry was correlated to precipitate surface fraction, density, and size distribution. For carbides, the work was extended to shape - and composition-distributions.
All those measurements showed that those features which are most affected by alloy chemistry variations are the liquidus and solidus temperatures, on the one hand, and the eutectic and carbide surface fractions and densities, on the other hand.
KeywordsDifferential Thermal Analysis Solidification Behaviour Carbide Precipitation Precipitation Temperature Quantitative Metallography
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