Effects of Primarily Solidified Dendrite and Thermal Treatments on the M23C6 Precipitation Behavior of High-Chromium White Iron

Young-Gy Song,Je-Hyun Lee,Jun-Seok Oh,Baig-Gyu Choi,Chang-Yong Jo

doi:10.3390/met11111690

Young-Gy Song, Je-Hyun Lee + Show 3 more

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https://doi.org/10.3390/met11111690

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Abstract

The precipitation behavior of M23C6 carbide during thermal treatment of high-Cr white iron with various fractions of primarily solidified dendrite was studied and reviewed. M23C6 precipitation in the primarily solidified dendrite occurred preferentially during conventional heat treatment, whereas it occurred scarcely in the eutectic austenite. The reaction between M7C3 and austenite caused the dissolution of M7C3 into austenite, followed by precipitation of M23C6 along the periphery of eutectic M7C3. Relatively low-temperature thermal treatment (modified heat treatment) led to precipitation of M23C6 particles in the eutectic austenite, which is presumed to be caused by solubility difference depending on temperature.

Highlights

Led to precipitation of M23 C6 particles in the eutectic austenite, which is presumed to be caused by solubility difference depending on temperature
M7 C3 carbides contribute to improving the wear resistance of the alloy; those primarily precipitated from the melting process ahead of eutectic reaction are known to be quite deleterious to impact toughness and should be avoided [1]
Phase prediction was carried out to understand the phase evolution during cooling, with the chemical composition provided in Table 2 through commercial software ThermoCalc (Thermo-Calc 2019b) on the basis of database

Summary

Introduction

Led to precipitation of M23 C6 particles in the eutectic austenite, which is presumed to be caused by solubility difference depending on temperature. The superior wear resistance of these alloys is originated in their matrix microstructure and the existence of various carbides, both in as-cast and heat-treated conditions. As-cast highCr white irons may have martensitic or austenitic matrix depending on the post-casting cooling rate and section size. The matrix structure and existing carbides have strong effects on the mechanical properties of high-Cr white cast irons. The carbides in high-Cr white iron are very hard and wear resistant but very brittle [1]. M7 C3 carbides contribute to improving the wear resistance of the alloy; those primarily precipitated from the melting process ahead of eutectic reaction are known to be quite deleterious to impact toughness and should be avoided [1]. Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations

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