The effect of boron on microstructure and mechanical properties of high-strength cast FeCrVC

This work describes the effect of small boron additions (0.01, 0.05 and 0.1 wt%) on the microstructure and mechanical properties of a high strength Fe92.7Cr4.2V2.1C1 (wt%) alloy prepared by applying relatively high cooling rates and pure preparation conditions. The special manufacturing process promotes the formation of martensite, retained austenite and MC (M=V, Cr) carbides and leads to excellent properties under compressive and abrasive loading already in the as-cast state, so that a time-consuming and expensive heat-treatment is not required. Due to microalloying with boron, these properties can be further improved by microstructural changes. Thereby, an increase of the martensite and a drop of the austenite volume fraction was detected by X-ray diffraction (XRD). Furthermore, boron additions lead to the formation of (Fe,M)3(B,C) carbides, which were verified by a combination of electron backscatter diffraction (EBSD) and dispersive X-ray spectroscopy (EDS/WDS) as well as transmission electron microscopy (TEM). With increasing amount of boron, these carbides form an interlocking network-like structure with the MC carbides, which leads in combination with the rising martensite fraction to FeCrMoVBC alloys showing significantly improved abrasive wear resistance and increased hardness compared to the Fe92.7Cr4.2V2.1C1 base alloy. Altogether, microalloying of the FeCrVC alloy with boron combined with a tailored casting process presents a fast and cost-effective method to enhance the performance of the alloy for the application as cutting and forming tool material.