Consider the gas carburizing of a gear of 1018 steel (0.18 wt %) at 927°c (1700°f). calculate the time necessary to increase the carbon content to 0.35 wt % at 0.40 mm below the surface of the gear. assume the carbon content at the surface to be 1.15 wt % and that the nominal carbon content of the steel gear before carburizing is 0.18 wt %. d (c in  iron) at 927°c = 1.28  10-11 m2 /s.

t = 56.6 min

Explanation:

Fick's second law is used to calculate time required for diffusion

where

= 1.15%

= 0.18%

= 0.35%

x = 0.40 mm = 0.0004 n

therefore we ahave

from error function table we hvae following result

for erf z                          z

     0.8209                      0.95

      0.8247                   x

      0.8427                    1

therefore

x = 0.959

thus

t = 56.6 min

can you make it more obvious. i can't see it properly