Fluidized-Bed Nitridation of Stainless Steel Powder
Titel:
Fluidized-Bed Nitridation of Stainless Steel Powder
Auteur:
Wang, Tsai-Chen Kimura, Shoichi
Verschenen in:
Materials and manufacturing processes
Paginering:
Jaargang 12 (1997) nr. 2 pagina's 275-290
Jaar:
1997-03-01
Inhoud:
An attempt was made to produce high-nitrogen stainless steel powder, that can be consolidated into a solid compact with uniform, high-nitrogen concentration. The nitridation of 316L stainless steel powder of average particle size of 70 μn with a minimum fluidization velocity of 4.5 cms-1, was nitrided in a 55 mm I.D. fluidized-bed reactor at temperatures ranging from 550°C to 750°C using NH3/H2 gas mixtures. NH3 concentration and temperature had pronounced effects on the progress of nitridation while the effect of H2 was minor. Nitrogen contents reached as high as about 10% by mass, completely converting Cr and Fe into CrN and Fe4N, at temperatures below 600°C. Only Cr was nitrided to form CrN at 750°C, reaching a saturated level of 6% nitrogen by mass. A nitrided shell was always developed on the particle, resulting from the precipitation of CrN, that progressed inward.
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