Effect of Ti-V-Nb-Mo addition on microstructure of high chromium cast iron

• Published in: China foundry Vol. 9; no. 2; pp. 148 - 153
• Main Authors: Ma, Youping, Li, Xiulan, Liu, Yugao, Zhou, Shuyi, Dang, Xiaoming
• Format: Journal Article
• Language: English
• Published: School of Metallurgic Engineering, Xi'an University of Architecture & Technology, Xi'an 710055, China%School of Mechanical and Electrical Engineering, Qingdao Agricultural University, Qingdao 266109, China 01.05.2012; Foundry Journal Agency
• Subjects: alloying; Carbides; Cast iron; Chromium; Diffusion; high chromium cast iron; kinetics; Microstructure; Thermodynamics; Titanium; Titanium carbide; thermodynamics; microstructure; alloying; high chromium cast iron; kinetics
• ISSN: 1672-6421; 2365-9459

The effects of trace additions of multi-alloying elements （Ti, Nb, V, Mo） on carbides precipitation and ascast microstructure of eutectic high chromium cast iron containing 2.85wt.%C and 31.0wt.%Cr were investigated from thermodynamic and kinetic considerations. The thermodynamic calculations show that Ti and Nb exist in the multi-alloying system in the forms of TiC and NbC. The formation of VC during the solidification is not feasible from the thermodynamic consideration. XRD analysis shows that the V exists in alloy compounds （VCr2C2, VCrFes）. The first precipitated high melting point particles （TIC, NbC） can act as the heterogeneous substrate of M7C3 carbides, which results in significant refinement of the M7C3 carbides. After the addition of alloying elements, C atom diffusion is hindered due to the strong affinities of the strong carbide forming elements for carbon, which decreases the growth rate of carbides. The combined roles of the increase of nucleation rate and the decrease of carbides growth rate lead to the finer microstructure.