Optimisation of sintering atmospheres for controlled sintering of PM steels

Paper in proceeding, 2013

The use of elements with high oxygen affinity such as Cr or Mn in PM steels has been met with skepticism although such grades are attractive options for structural applications. They require strict control of the used atmosphere during the sintering process. Various techniques such as photoacoustic spectroscopy (PAS) and continuous CO/CO2/H2O measurements have been implemented for atmosphere monitoring during sintering trials of Cr-alloyed steel powder. The used atmospheres were nitrogen-hydrogen blends (0,3,10 and 100% H2) as well as vacuum. The progress of the oxidation/reduction processes was also followed with thermogravimetric studies. The pressed and sintered samples were examined using optical and electron microscopy in combination with EDX in order to evaluate the formed reaction products. The presence of hydrogen, even in small amounts, is positive for the oxide reduction. Results show that careful adjustment of the used atmosphere leads to efficient production of steel components based on Cr - prealloyed powders.