Diffusion in material
You are hardening a very thick tool plate made of BCC Fe byincreasing the carbon concentration in its surface layer by heatingthe tool in the presence of a C-rich gas (e.g. methane) whichmaintains a constant C concentration at the surface. A heattreatment at 600 °C for 100 minutes results in a C concentration of0.75 wt% at a position 0.5 mm below the surface. How long would ittake to obtain the same result (i.e. the same C concentration atthe same depth) if the heat treatment were conducted at 900 °C.Schematically draw the C concentration profile (i.e. the Ccomposition as a function of the distance from the surface) in thetool plate. At either of the temperatures, does the diffusion rate(measured by the diffusion flux) go up or down with increasingdistance from the surface and why?
D0 = 2 x 10-6 m2/s andQd = 84 kJ/mol
