The C diffusion distance could be estimated from the change in fracture mode as a function of distance from the specimen surface. In addition, diffusion parameters such as the activation energy for C diffusion in Mo could be derived from Arrhenius plots of the C diffusion distance and the diffusion temperature. The fracture surfaces of Mo–Ti alloys after carburizing were examined here by using a scanning electron microscope. The effects of Ti additions upon the C diffusion behavior in Mo were then considered. It was first demonstrated that the C diffusion distance was decreased by adding Ti at a given diffusion temperature. Secondly, the activation energy for C diffusion in Mo–Ti alloys was smaller than that in pure Mo (figure 3). In addition, the critical C concentration for the transition of the fracture mode from intergranular to transgranular in Mo–Ti alloys was larger than that in pure Mo. These results were attributed mainly to preferential combination of a C atom and a Ti atom.

Effects of Ti Addition on Carbon Diffusion in Molybdenum. T.Inoue, Y.Hiraoka, M.Nagae, J.Takada: Journal of Alloys and Compounds, 2006, 414[1-2], 82-7

Figure 3

Diffusion Distance of C in Mo-Ti Alloys

(a: pure Mo, Mo-1%Ti, c: Mo-1.5%Ti)