Microstructure of the Working Layer of X46Cr13 Steel in a Bimetal System with Gray Cast Iron

The research conducted in this study aimed to determine whether the production of a layered casting in the material system of X46Cr13 steel (working part) and gray cast iron (base part) can be integrated with the hardening process of this steel within the conditions of the casting mold. Accordingly, a series of layered castings was produced by preparing the mold cavity, where a monolithic steel insert was poured with molten gray cast iron with flake graphite. The variable factors in the casting production process included the pouring temperature Tp and the thickness of the support part g. Importantly, given that the hardening of the X46Cr13 steel insert occurred directly within the mold, the selection of casting parameters had to balance the ability to heat the insert to the austenitization temperature Tγ≥950°C while also creating thermokinetic conditions conducive to the rapid cooling of the system. Therefore, chromite sand—commonly regarded as a rapid-cooling material—was selected as the matrix for the molding material. Based on the conducted studies, it was determined that the thermokinetic properties of this material allowed the surface of the cast working part to be heated to the austenitization temperature. The microstructure consisted of Cr(Fe) carbides within a martensitic-pearlitic matrix, with martensite filling the grains of the primary austenite and pearlite situated along their boundaries. The carbides were primarily located at grain boundaries and, to a lesser extent, within the primary austenite grains. Through transmission electron microscopy and X-ray diffractometry, the type of Cr(Fe) carbide in the microstructure of the working part was identified as M23C6.