Exploring the Solidification Sequence and Solid-State Transformations in High-Boron Multi-Component Cast Alloys by Differential Scanning Calorimetry

The newly designed multi-component (Fe–5 wt.% W–5 wt.% Mo–5 wt.% V–10 wt.% Cr–2.5 wt.% Ti) cast alloys, containing 0.7–1.1 wt.% C and 2.7–3.6 wt.% B, are intended for tribological applications. The present work was aimed at studying the solidification sequence and phase transformation temperature intervals of the above-mentioned alloys, in order to elucidate their structural status and further develop an appropriate heat treatment regime. For this purpose, Differential Scanning Calorimetry (DSC), microstructure observation and thermodynamic modeling were applied. Two temperature ranges of exothermic reaction (caused by the release of latent heat during transformation) were revealed at 1200-1091  °C and ≤400 °C. The first range was caused by the primary carboboride (M(C,B), M₂(B,C)₅) precipitation, followed by sequential eutectic reactions with the formation of carboborides M₂(B,C)₅, M₇(C,B)₃, and M₃(C,B). The temperature ranges of eutectic transformations decreased with the increase in carbon and boron contents. Low-temperature exothermic reactions (at 399-181 °C) referred to the transformation of austenite into bainite or martensite. The values of the latent heat of the transformations were calculated and discussed.