Abstract

The as-cast microstructure of Fe-Cr-C-V white irons consists of M7C3 and vanadium rich M6C5 carbides in austenitic matrix. Vanadium changed the microstructure parameters of phase present in the structure of these alloys, including volume fraction, size and morphology. The degree of martensitic transformation also depended on the content of vanadium in the alloy. The volume fraction of the carbide phase, carbide size and distribution has an important influence on the wear resistance of Fe-Cr-C-V white irons under low-stress abrasion conditions. However, the dynamic fracture toughness of Fe-Cr-C-V irons is determined mainly by the properties of the matrix. The austenite is more effective in this respect than martensite. Since the austenite in these alloys contained very fine M23C6 carbide particles, higher fracture toughness was attributed to a strengthening of the austenite during fracture. Besides, the secondary carbides which precipitate in the matrix regions also influence the abrasion behaviour. By increasing the matrix strength through a dispersion hardening effect, the fine secondary carbides can increase the mechanical support of the carbides. Deformation and appropriate strain hardening occur in the retained austenite of Fe-Cr-C-V alloys under repeated impact loading. The particles of precipitated M23C6 secondary carbides disturb dislocations movement and contribute to increase the effects of strain hardening in Fe-Cr-C-V white irons.

Highlights

  • The as-cast microstructure of Fe–Cr–C–V white irons consists of M7C3 and vanadium rich M6C5 carbides in austenitic matrix

  • The aim of this paper is to review the microstructural characteristics and properties relevant to the service performance of hypoeutectic Fe–Cr–C–V white cast irons, namely the hardness, abrasion wear resistance, fracture toughness and repeated impact resistance

  • The results obtained by examination of impact resistance* of Fe–Cr–C–V white irons in as-cast conparticles, higher fracture toughness was attributed to a strengthening of the austenite during fracture [29]

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Summary

REVIEW PAPER

High chromium white cast irons are an important class of wear resistance materials currently used in a variety of applications where stability in an aggressive environment is a principal requirement, including the mining and mineral processing, cement production, slurry pumping and pulp and paper manufacturing industries. The addition of an alloying element which confines carbon in the form of a carbide different from cementite, with a greater hardness and more favorable morphology, and which reduces the carbon content of the matrix, allows the simultaneous improvement of both toughness and abrasion resistance [2,21,25,26,29]. Cerium has limited solubility in austenite and M7C3 eutectic carbide [25, 43, 44] This element formed inclusions in high chromium white irons [45, 46]. The aim of this paper is to review the microstructural characteristics and properties relevant to the service performance of hypoeutectic Fe–Cr–C–V white cast irons, namely the hardness, abrasion wear resistance, fracture toughness and repeated impact resistance

MICROSTRUCTURAL DEVELOPMENT
Microstructure after subcritical heat treatment
Findings
CONCLUSIONS
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