Heat Treatment Featuring the Key-Parameters of High Chromium White Cast Iron Microstructure

Abstract

The high chromium white cast iron (HCWCI) has been on the scene for decades, with expectations to remain there due to its exceptional wear resistance. HCWCI is mostly applied as-cast, but it can also be used as a coating material. The carbides in HCWCI microstructure, whose composition depends on alloying and heat treatment regime, give this special feature to white cast irons. The investigation presented in this paper was carried out by examining two HCWCI alloys, denoted HCWCI_1 and HCWCI_2, both alloyed with molybdenum in addition to high chromium content. The HCWCI_1 alloy contains 24.48% Cr with 1.32% Mo, and HCWCI_2 contains 14.11% Cr with 2.47% Mo. Comprehensive qualitative microstructural characterization was performed on all types of samples: as-cast samples, those obtained after quenching (at -196 °C) and/or quenching followed by tempering (at 250 °C). Besides standard etching procedures, the selective color etching was also applied here. The microstructure parameters, such as width of secondary dendritic arms and carbides size, are measured and correlated with applied alloy obtaining procedure and heat treatment regime, so they can be discussed in relation to the microconstituent’s ratio (such as ratio of different carbides) and morphology.