Mechanical and oxidation properties of high density sintered duplex stainless steels obtained from mix of water and gas atomised powders

High density powder metallurgy duplex stainless steels have been obtained by mixing water and gas atomised powders. AISI 434L water atomised ferritic powders were mixed with different percentages (up to 50%) of AISI 316L gas atomised powders. The mixtures were then compacted by uniaxial pressing and vacuum sintered at three temperatures. Physical and mechanical properties were measured, showing the positive influence of small size austenitic powders in density and strength. Best materials were submitted to oxidation tests at 800 and 900 degrees C. Mass gains during high temperature exposure have been dramatically reduced by the addition of gas atomised powders. Characterisation of the scales through scanning electron microscopy and X-ray diffraction has shown that the mixtures mainly comprise chromia, although other oxides have been detected.