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

The effect of carbon added in the form of either cast-iron powder or graphite on the sinterability of chromium steel was investigated. The growth and instability of volume change during sintering produced by cast-iron additions was explained as a result of a thermally activated after-effect in the solid phase, and the formation of FeCr2O4 around particles of Kh30. Substitution 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°C. Scatter in the degree of volume change was reduced from 1.5–2.0 to 0.1–0.3%. Iron-chromium material obtained with the use of graphite had improved strength properties as well as high produceability.