The influence of cooling rate on the structure and properties of castings of hypereutectic high-chromium cast iron when they are modified with B, Bi, Sb, Sn, Ca

The article presents the results of a study of the influence of B, Bi, Ca, Sn, and Sb additives on the structure, composition, and properties of individual phases and mechanical properties of castings made of hypereutectic high-chromium cast iron (HCCI), similar in composition to G-X300CrMo27-1 cast iron. Additives of these elements were introduced into the melt before cooling at an amount of 0.2 wt.%. The ingots were obtained at a melt cooling rate in the crystallization range of 0.083–0.116 ℃/s and at 4.67–5 ℃/s. When studying the structure, the parameters and proportion of primary carbides, and the proportion of eutectic carbides were determined and a description was given of the change in the austenitic matrix. Using microprobe analysis and microhardness measurements, changes in the composition and hardness of primary, eutectic carbides and the matrix were determined. Hardness HV, bending strength, and abrasive wear resistance were determined. It has been shown that depending on the cooling rate, the effect of these additives on the structure and properties of castings changes. The mechanism of influence of these elements on the process of crystallization of primary carbides in HCCI is considered. Based on the data obtained, it is proposed to use Ca as a modifying additive when producing castings from HCCI of a hypereutectic composition under slow cooling conditions, and B under fast cooling conditions. This makes it possible to increase the wear resistance of castings.