Temperature Dependence of Sand-Erosion Rate of 25% Chromium-Boron White Cast Iron

The γ+M2B, γ+M23(C, B)6 and γ+M7(C, B)3 eutectics solidify by itself or jointly at compositions along the pseudo-binary eutectic line in a Fe-25%Cr-C-B system. Due to this, various eutectic alloys with some kinds of eutectic structures were obtained by changing the combination of carbon and boron content. Sand-erosion tests were carried out in two kinds of slurries with tap water or seawater, in order to examine the effect of corrosion resistance on six kinds of Fe-25%Cr-C-B eutectic alloys. The sand-erosion rate (Wk) was shown by the formula, Wk=Kexp(−Q⁄RT) where K: constant, Q: apparent activation energy, R: gas constant and T: slurry temperature. The Q value obtained from this formula for each specimen ranged from 3 to 20 kJ/mol in the tap water solvent slurry and from 4 to 40 kJ/mol in the seawater solvent slurry. The variation in Q due to the difference of the slurry solvents can tentatively be arranged into three types; (I) constant, (II) increase and (III) decrease. The Q value and the Wk level were found to be a useful criteria for sand-erosion resistance. The change in Wk in the tap water solvent slurry was estimated to be little in each alloy, whereas in the seawater solvent slurry the Wk values of the alloys containing 2%B were 1⁄15∼1⁄30 of the SUS430-type stainless steel and boron free alloys.