Modification of Grey Cast Iron by Compositions Based on Nano-Disperse Powders of Tungsten and Titanium Carbides

Abstract

Experiments involving modification of cast iron manufactured in China which is similar to Russian grades (SCh-18 – SCh-30) using the compositions based on a mixture of tungsten and titanium carbides were carried out. Nanodispersed carbide powders were obtained by means of self-propagating high-temperature synthesis (SHS) in combination with preliminary mechanical activation (MA). The studied modifying agents were WС:TiС = 70:30 with protector metals: chromium (50/50, M1 modifying agent); chromium and copper (25/25/50, modifying agent M2) within the range of concentrations of the ceramic phase – 0.01-0.2%; the modifying agents were introduced into the casting mold and into foundry ladle. Two designs of casting molds were studied. The use of modifying agents for intra-mold modification may lead to an increase in the tensile strength up to 18.5%, relative corrosion stability in hydrochloric acid up to 58.8%. After modification in ladle, the strength of the samples increased to 25-29% only after storage for 3.5 months. The results provide evidence that the studies of grey cast iron modification by the agents containing nanodispersed ceramic phases (WС, TiС) should take into account not only the concentrations and composition of modifying agents but also various technological parameters (design, mold volume, method of introduction of the modifying agent etc.)