| The plasma rotating electrode process was applied to the production of type 304 and 316 stainless steel powders in order to determine the effect of operating conditions on the particle size and its distribution, and to analyze their microstructures, cooling rate and relative amount of ferrite phase for the as-prepared powders. For the operating conditions of plasma arc current : 140∼240 A and anode rotating speed : 17,500∼25,000rpm, stainless steel powders produced showed the typical bimodal size distribution ranging 50∼425㎛ and mean volume-surface diameter ranging 143∼238㎛. The appearances and microstructures of powders were found to be solidified with cellular or dendrite structures which have being depended on cooling rate(particte size). The estimated cooling rate of powders ranging 150 to 50㎛ in size was about 10³∼10^5K/s. The weight traction of ferrite phase in type 316 powders was found to be increased with decreasing particle size, due to the difference in the solidification behavior. For type 304 powders, however, the ferrite phase was not detected by X.R.D. |
|
