Refinement of primary carbides in hypereutectic high-chromium cast irons: a review
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Refinement of primary carbides in hypereutectic high-chromium cast irons: a review Abhi-Shek Jain1, Haiwei Chang1, Xinhu Tang1,2,*, Brook Hinckley2, and Ming-Xing Zhang1,*
1 2
School of Mechanical and Mining Engineering, University of Queensland, Brisbane, QLD 4072, Australia Weir Minerals Australia Ltd, Artarmon, NSW 2064, Australia
Received: 27 May 2020
ABSTRACT
Accepted: 19 August 2020
As a category of crucial wear-resistant alloys, high-chromium cast irons (HCCIs) are widely used in mining, minerals and cementation industries. The large volume fraction of coarse primary M7C3 carbides (PC) imparts excellent wear resistance. However, coarse carbides also induce brittleness, resulting in high cracking susceptibility, and early failure of components, particularly under impact. To minimize the brittleness and increase the service life of HCCI parts, different techniques have been developed through modifying the carbide morphology and refining its size. This paper comprehensively reviews the currently available methods that have either been used in industry production or in laboratory development to modify the primary M7C3 carbides in various HCCIs. The possible mechanisms that govern the refinement of primary carbides are also discussed in-depth. Based on previously published work, the mechanical performance of HCCIs is correlated with the microstructure of the matrix, and with the size, shape, volume fraction and distribution of primary carbides. This may provide solid fundamental to develop more effective techniques and/or new alloys to further improve the properties of this type of materials, increasing their engineering service life and to tailor their wider applications. In addition, the present work also seeks theoretical feasibility to apply the recently well-established theories/models of grain refinement for cast metals to refinement of the primary carbides in HCCIs.
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Springer Science+Business
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Handling Editor: P. Nash.
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https://doi.org/10.1007/s10853-020-05260-8
J Mater Sci
Introduction On solidification of cast irons containing over 2 wt.% carbon and other alloying elements, carbide rather than graphite, forms, which enables a silver colour (white) fracture surface, and the alloy is named as ‘‘white’’ cast iron [1, 2]. Formation of such carbide results in the high hardness and superior wear resistance of this type of materials. The volume fraction, type and morphology of the carbide rely on the carbon content and the alloying elements contained in it. In case of hypoeutectic cast irons (the carbon content is below the eutectic point, * 2.5–4.1 wt.%), majority of the carbide is eutectic carbide in lamellar morphology. In hypereutectic cast irons, both Widmansta¨tten primary carbide and eutectic carbide form. Addition of chromium greater than 12 wt.% forms high-chromium cast irons [3]. It is known that the high chromium not only leads to improved corrosion resistance due to
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