Influence of Vanadium Content on Continuous Cooling Transformation Behavior of Multi-component White Cast Iron

Abstract

  Influence of V content in multi-component white cast iron, which contains 5 mass% main alloying elements of Cr, Mo, W, each and 2 mass% of C and Co, on continuous cooling transformation behavior was investigated by varying the V content from 3 mass% to 9 mass%. The austenitizing temperatures used in this experiment were 1273 K and 1373 K.
  In the irons with up to 7 mass%V, both pearlite and bainite transformations appeared in CCT diagram, but in the iron with 9 mass%V, only transformation of ferrite precipitation was seen.
  The critical cooling rate of pearlite transformation (V _C-P) decreased from 0.56 K/s to 0.11 K/s at 1273K austenitization and from 0.43 K/s to 0.06 K/s at 1373 K austenitization respectively, as the V content increased up to 7 mass%. The critical cooling rate of bainite transformation (V _C-B) decreased with an increase in V content up to 4 mass%, but it increased over 4 mass%V.
  Though the Ms temperature did not change much between the irons with 3 mass%V and 4 mass%V, it gradually rose with an increase in the V content over 4 mass%, regardless of the austenitizing temperature. Mf temperature appeared first in the 5 mass%V iron at 1273K austenitization and in the 7 mass%V iron at 1373K austenitization, respectively, and then it rose corresponding to the increase of the V content.
  The highest macro-hardness of transformed specimen increased once and then gradually decreased as the V content increased. The V content at the maximum hardness was about 5 mass%.