Abstract
The formation of Cr-Al diffusion coated layer was studied on 18Cr/10 Ni/Ti austenite stainless steel. The specimens of the steel were treated in HCl atmosphere by powder pack process with a diffusion coating agent composed of the mixture of Al and Cr powders. The results obtained were as follows: (1) The leading factors controlling the formation of Cr-Al diffusion coated layer, which were different from those controlling the formation of the layer of one element, were as follows: (a) Deposition rates of the two elements, (b) Deposition velocity of coating elements, (c) Mutual diffusion coefficient, (d) Time for diffusion coating. (2) Mean deposition rate of Al, deposition velocity of coating elements, and mutual diffusion coefficient increased; but mean deposition rate of Cr decreased with the increase of Al quantity in the diffusion coating agent. (3) Mean deposition rate of Cr, deposition velocity of coating elements, and mutual diffusion coefficient increased; but mean deposition rate of Al decreased with the rise of treating temperature. (4) Mean deposition rate of Cr increased; but deposition velocity of coating elements and mean deposition rate of Al decreased with the increase of treating time. (5) Mean deposition rate of Al was higher; but mean deposition rate of Cr and deposition velocity of coating elements were lower in argon atmosphere as compared with in hydrogen atmosphere. (6) The tendencies of mean deposition rates well corresponded with those of surface concentrations of specimens.
