Carbide-Dispersion Carburizing of Fe-Ti Alloys

Carburizing of ferritic alloys containing substitutional solute such as Ti or V having a high affinity for carbon yields carbide-dispersed layer (CD layer) under a similar mechanism to the internal oxidation.In this work, the kinetics of carbide-dispersion carburizing (CD carburizing) of Fe-Ti alloys containing up to 3.85 mass%Ti has been investigated at temperatures between 923 and 1023 K. A CD layer grows in proportion to the square root of time and the growth rate was explained by a kinetic equation proposed by Wagner for the internal oxidation. The carbide produced in a CD layer has been identified to be TiC by X-ray analysis, and the morphology of the carbide has been studied by electron microscopy. The particle size of carbide increased lineally with depth from the specimen surface. The hardness of a CD layer increased with increasing Ti content, and reached Hv 770 at about 3 mass%Ti. No further increase in hardness was observed in the alloys with higher Ti content, because the solubility of Ti in α-Fe was limited.