Titanium carbonitrides in steels alloyed with tungsten and molybdenum

Conclusions

The possibility of tungsten dissolving in titanium carbonitride present in the steel is confirmed by two factors: 1) the solubility of tungsten in titanium carbide, established in the binary WC-TiC system [4–7]; 2) the existence of four phases with the same type of structure and similar lattice constants in the Ti−W−C−N system (a=4.33 Å for TiC,a=4.24 Å for TiN,a=4.27 Å for W₂C,a=4.126 Å for W₂N [7]).

Considering the affinity of tungsten and molybdenum and their interchangeability in carbides of other types, one would expect partial replacement of titanium, with molybdenum in carbonitrides. The solubility of tungsten and molybdenum in titanium carbonitride was demonstrated in two steels of different types — austenitic steel 417455 and pearlitic steel T 67. In steel T60 with 13% Cr, however, neither tungsten nor molybdenum was found in the carbonitride. Consequently, it can be assumed that the solution of tungsten and molybdenum in Ti(C, N) is also determined by the properties of the metallic matrix and the treatment or primary cooling conditions of the steel. This determines whether or not tungsten or molybdenum partially replaces titanium in carbonitride.