Effect of vanadium on microstructure and wear resistance of Ni–Cr alloyed cast iron

Abstract

The effect of vanadium content on the microstructure of Ni–Cr alloyed cast iron has been investigated by optical and scanning electronic microscopy and differential scanning calorimetry, aided by thermodynamic calculations of the phase diagrams. The wear resistance of cast and tempered specimens was examined in pin on disc tests. The results show that with increasing V additions, the number of vanadium carbide (VC) precipitates was greatly enhanced and the distribution of precipitates became more uniform. Furthermore, refinement of M₃C precipitates (M = Fe, Cr, Ni, Mo, V) increased with V addition as a result of heterogeneous nucleation at VC particles. An increase in V content from 0·85 to 4·58 wt-% improved the wear resistance of the cast iron significantly, by a factor of almost 13. Analysis of the microstructure suggests that the refinement of M₃C and the uniform distribution of dense VC particles account for the improvement of wear resistance of the cast iron.

Keywords:

• Ni–Cr alloyed cast iron
• Microstructure
• Vanadium
• Carbide
• Hardness
• Wear resistance

We greatly appreciate anonymous reviewers and Dr M. Hull whose constructive comments have improved the quality of our paper. This work is financially supported by the China Postdoctoral Science Foundation (grant no. 20060390771), the Natural Science Foundation of Hebei Province (grant no. E2007000382), the Key Technologies R&D Program of Hebei Province (grant no. 07212109D) and Qinhuangdao Science and Technology Research and Development Program (grant no. 2012021A060).