SYNTHESIS OF NANO-STRUCTURED DUPLEX AND FERRITIC STAINLESS STEEL POWDERS BY DRY MILLING AND ITS COMPARISON WITH WET MILLING

In the present paper, elemental Fe, Cr and Ni powders were used to fabricate nano-structured duplex and terrific stainless steel powders by using high energy planetary ball milling. We have studied the effect of milling atmosphere like wet (toluene) and dry (argon) milling of elemental Fe-18Cr-13Ni (duplex) and Fe-17Cr- 1Ni (ferritic) powders for 10 h in a dual drive planetary mill. Stearic acid of 1 wt. % was added during milling to avoid agglomeration. The dry and wet milled duplex and ferritic stainless steel powders were characterized by XRD, SEM and particle size analysis techniques. We have found that both the milling atmospheres have great influence in controlling the final particle morphology, size and phase evolution during milling. It was reported that dry milling is more effective in reducing particle size than the wet milling. The Nelson-Riley method of extrapolation was used to calculate the precise lattice parameter and Williamson-Hall method was used to calculate the crystallite size and lattice strain of both the stainless steel milled in argon atmosphere. Dry milled duplex and ferritic stainless steel were then consolidated by conventional sintering method at 1100, 1200 and 1300 degrees C temperatures under argon atmosphere for 1 hour.