Carbide and Matrix Microstructure Evolution of High-Vanadium Wear-Resistance Cast Iron with High-Silicon Content During Austempering

The nanobainite microstructure was fabricated on the high-vanadium cast iron with high silicon content, and the measures of casting and austempering were taken. The results showed that the as-cast microstructure is mainly composed of VC, M7C3, Fe3C, ferrite, and austenite. After austempering, the acicular M2C-type carbides precipitated from skeletal M7C3-type carbides, causing a decrease in Cr content in M7C3 and the morphology change of M7C3, and the molecular formula of M7C3 changed from the (Fe0.61Cr0.19Mo0.12V0.06Mn0.02)7C3 to the (Fe0.41Cr0.36Mo0.09V0.11Mn0.03)7C3, and the morphology of M7C3 changes from skeletal shape to net shape. There is no apparent change in the morphology and chemical composition of VC. And the transformation of the matrix microstructure from pearlite to a mixed structure of bunchy nanobainite and retained austenite happened. It turned out that the thickness of bainite ferrite and the film retained austenite is 50–110 nm and 30–90 nm, respectively.