A time-temperature-transformation (TTT) diagram, with respect to the formation of intermetallic phase in the range from 700 ЊC to 1000 ЊC, has been assessed by point counting for a recently developed 29Cr-6Ni-2Mo-0.38N superduplex stainless steel (SDSS). Using a computer program previously developed by the authors, a continuous cooling-transformation (CCT) diagram was calculated from the TTT diagram, assuming that the transformation can be described by an Avrami-type equation. Controlled cooling experiments were made to confirm the validity of this computer model. Mechanical testing showed that the minimum acceptable impact toughness of 27 J corresponded to 5 vol pct of intermetallic phase. A comparison of impact toughness to hardness showed that toughness was a very sensitive measure of intermetallic phase formation, while hardness was insensitive and showed no significant increase until the material was catastrophically brittle. The thermodynamic computer program Thermo-Calc was used to predict microstructures and compare microstructures obtained after aging for 72 hours. It was found that this program could be used in a qualitative manner for predicting microstructural changes at various temperatures, but was unable to predict variables such as dissolution temperature and volume percentage with precision. The intermetallic phase was found to consist entirely of tetragonal phase with a P4 2 /mnm crystal structure. The absence of phase as a precursor of phase provided an explanation for the delayed formation of intermetallic phase, as compared to that of more molybdenum-rich SDSSs.

A small-scale microwave convective dryer was built to study the effects of microwave power level, air temperature, and air velocity on drying kinetics, temperature development, and specific energy consumption (MJ/kg evaporated water) using statistical designs. Increased microwave power had a large significant effect on moisture loss and temperature development and it reduced specific energy consumption. Increased air temperature and air velocity increased specific energy consumption, as their effect on drying kinetics was smaller in the system used. Low air temperature slowed the drying process, without affecting the relationship between average sample temperature and average moisture content during drying.

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