HRPD AND TEM STUDY OF P/M 58Fe17Cr25Ni AUSTENITIC STAINLESS STEEL SYNTHESIZED BY SPARK PLASMA SINTERING

In this study, 58Fe17Cr25Ni austenite stainless steel has been fabricated using metal powder through sintering with a spark plasma at temperatures of 900 and 950 degrees C for a time of 5 minutes. High purity Fe, Ni and Cr powders were used as materials for this steel. Before sintering, the powder was mixed in a milling equipment which was processed for 5 hours, then it formed into a coin by pressing it under a load of 25 tons. The microstructure and phases in the 58Fe17Cr25Ni austenite stainless steel were characterized through an optical microscope, a scanning electron microscope, a transmission electron microscope, with the last two devices equipped with an energy dispersion spectrometer. High resolution powder neutron diffractometer was also used for identifying the crystal structure in the 58Fe17Cr25Ni austenitic stainless steel. The sintering process at temperatures of 900C and 950 degrees C generally forms microstructure having matrix of equiaxed austenite grains, with a crystal structure of face-centered cubic which included in the Fm3m space group. Some particles with high Cr content, alpha '-Cr, are distributed in all austenite grains. In more detailed observations, the austenite grains seen in the 58Fe17Cr25Ni austenitic stainless steel sintered at 900 degrees C are twin grains. Dislocations, slip planes and bands are also existed in those grains. These defects are expected to decrease with increasing sintering temperatures up to 950 degrees C. This change was followed by the appearance of air bubbles and sub-grains as the dominant sub-structures in the 58Fe17Cr25Ni austenitic stainless steel sintered at 950 degrees C.