Effect of carbon on volume changes during the sintering of an iron-chromiuim material

The effect of carbon added in the form of either cast-iron powder or graphi te on the sinterability of chromium steel was investigated. The growth, and instability of volume change during sintering produced by cast-iron additi ons was explained as a result of a thermally activated after-effect in the solid phase, and the formation of FeCr2O4 around particles of Kh30. Substit ution of graphite for cast iron in the powder charge prevented oxidation of the chromium-rich particles, and resulted in low and stable shrinkage (0.1 -0.8%) after sintering in the range 750-1250 degrees C. Scatter in the degr ee of volume change was reduced from 1.5-2.0 to 0.1-0.3%. Iron-chromium mat erial obtained with, the use of graphite had improved strength properties a s well as high produceability.