Effects of Nano-Y2O3 and Sintering Parameters on the Fabrication of PM Duplex and Ferritic Stainless Steels

Abstract

Here we report the effects of nano-Y2O3 addition, sintering atmosphere and time during on the fabrication of PM duplex and ferritic stainless steels composites by dual-drive planetary milling of elemental Fe, Cr and Ni powders followed by conventional pressureless sintering. Yttria-free and yttria-dispersed duplex and ferritic stainless steels are fabricated by conventional sintering at 1000, 1200 and 1400 °C temperatures under argon atmosphere. In another set of experiment, yttria-free and yttria-dispersed duplex and ferritic stainless steels are consolidated at 1000 °C for 1 h under nitrogen atmosphere to study the effect of sintering atmosphere. It has been found that densities of duplex and yttria-dispersed duplex stainless steel increase from 71% to 91% and 78% to 94%, respectively, with the increase in sintering temperature. Similarly, hardness value increases from 257 to 567 HV25 in case of duplex, and from 332 to 576 HV25 in yttria-dispersed duplex stainless steel. X-ray diffraction analysis shows the domination of more intense austenite phase than ferrite at higher sintering temperature and also in nitrogen atmosphere. It is also evident that addition of yttria enhances phase transformation from α-Fe to γ-Fe. Duplex and yttria-dispersed duplex stainless steels exhibit the maximum compressive yield strength of 360 and 312 MPa, respectively.