Diffusion and solubility of carbon in molybdenum and TZM

The kinetics of decarburisation of molybdenum and TZM have been studied by quadrupole mass spectrometry over the temperature range 1260-20100 C. Flat and cylindrical samples were heated under a few 10-6 Torr 02. The outgassing flow of the carbon monoxide product as a function of time is controlled by the diffusion of carbon. Alloying with titanium and zirconium (TZM alloys) reduces the diffusion of carbon but increases its solubility below 17000C. The decarburisation is accompanied by internal oxidation which does not appear below 20000C in molybdenum. Anomalies in the diffusion of carbon can be attributed to the carbon becoming dissolved in the precipitated titanium oxide. (author)