X-ray and electron microscopic investigations of 16–25 and 18–40 type alloys

Conclusions

• 1. In low-carbon Fe\t-Cr\t-Ni alloys (16% Cr; 25% Ni and 16% Cr; 40% Ni) containing different amounts of tungsten the excess phases are not only niobium carbides and titanium carbonitrides but also the Laves phase and the double carbides.

• 2. Niobium affects the process of phase formation differently than tungsten: an increase in the concentration of tungsten greatly increases the amount of the secondary Laves phase but increases very little the amounts of double carbides or the primary Laves phase.

  The increase in the amount of niobium (or titanium) is accompanied by an increase in the amount and size of the primary Laves phase, while the amount of the secondary Laves phase decreases. Also, an increase in the concentration of titanium leads to the occurrence of secondary phases rich in nickel, titanium, and aluminum: Ni₃Ti and α^′-phase.

• 3. An increase of the amount of nickel with a corresponding decrease of the amount of iron decreases the amounts of the primary and secondary Laves phases.