抄録
The effects of various treatment conditions such as H2 flow rate, time, particle size etc. on Cr diffusion coating by powder method were studied. The behavior of the surface layer was discussed with respect to the weight increase of specimens by reducing reaction.
The results obtained and considerations were as follows:
(1) Since a reversible relation was found between the generating reaction of CrCl2 and the reducing reaction for Cr deposition, the maximum value appeared in the H2 flow rate (partial pressure of H2) for the weight increase by the equilibrium between the both reactions.
(2) The reaction rate was higher with the decrease of Cr particle size in the diffusion agent and was determined by the step of gas diffusion. On the other hand, the rate was determined by the step of chemical reaction rate for coarse particles.
(3) Since the weight increase of specimens was caused by exchange reaction, not by reducing reaction, the specimens having higher content of iron showed smaller increase of weight.
