High chromium white irons are ferrous based alloys containing 11–30 wt-% chromium and 1.8–3.6 wt-% carbon, with molybdenum, manganese, copper, and nickel sometimes added as additional alloying elements. The microstructure of these alloys typically consists of hard primary and/or eutectic carbides in a matrix of austenite or one of its transformation products. The presence of hard alloy carbides results in excellent abrasion resistance and, consequently, these alloys are commonly used for materials handling in the mining and minerals processing industries. Alloy content, solidification parameters, and thermal processing can dramatically alter the microstructure that is produced, and this in turn can influence the properties and hence performance of white iron alloys during service. This review outlines the development of the microstructure in high chromium white irons through solidification and thermal processing. The metallurgical effects of conventional processing techniques are discussed, and ad...

Microstructure-property relationships in high chromium white iron alloys

Superior abrasive wear resistance, combined with relatively low production costs, makes high Cr white cast irons (WCIs) particularly attractive for applications in the grinding, milling, and pumping apparatus used to process hard materials. Hypoeutectic, eutectic, and hypereutectic cast iron compositions, containing either 15 or 26 wt pct chromium, were studied with respect to the macrostructural transitions of the castings, solidification paths, and resulting microstructures when poured with varying superheats. Completely equiaxed macrostructures were produced in thick section castings with slightly hypereutectic compositions. High-stress abrasive wear tests were then performed on the various alloys to examine the influence of both macrostructure and microstructure on wear resistance. Results indicated that the alloys with a primarily austenitic matrix had a higher abrasion resistance than similar alloys with a pearlitic/bainitic matrix. Improvement in abrasion resistance was partially attributed to the ability of the austenite to transform to martensite at the wear surface during the abrasion process.

Solidification structure and abrasion resistance of high chromium white irons

Selective laser melting of TiC reinforced 316L stainless steel matrix nanocomposites: Influence of starting TiC particle size and volume content

The effect of heat treatment temperature on the microstructure and mechanical properties of a Fe–4.0C–18.0Cr–1.0Mo–1.0Ti (wt.%) hypereutectic high chromium white cast iron was investigated. The response of the alloy to heat treatment and, therefore, the microstructures developed, differed significantly. With the increase of the heat treatment temperature, the precipitated secondary carbides changed from M 3 C to M 7 C 3 and the retained austenite content increased. With the increase of the heat treatment temperature, the bulk hardness and matrix microhardness both increased and reached peak values of 64.6 HRC and 850 HV, respectively at the temperature of 1000 °C. But they all decreased at the heat treatment temperature of 1050 °C. The impact toughness of the alloy increased significantly compared with the conventional cast hypereutectic high chromium white iron (containing 4.0 wt.% C and 17.0 wt.% Cr) without titanium and inoculation and its value was in the range of 6.1–6.9 J/cm 2 , but it did not change very much with the increase of heat treatment temperature.

Effect of heat treatment on microstructure and mechanical properties of a Ti-bearing hypereutectic high chromium white cast iron

Effects of deep cryogenic treatment on property of 3Cr13Mo1V1.5 high chromium cast iron

The influence of a range of austenitizing and subcritical (tempering) heat treatments on the high-stress abrasion resistance and fracture toughness of four commercially significant grades of alloy white cast iron was investigated. Complementing an earlier study[1] on the influence of a more limited range of heat treatments on the gouging abrasion performance of the same alloys, the results showed that the effect of austenitizing temperature on high-stress abrasion pin test weight loss differed for each alloy. With increasing austenitizing temperature, these results ranged from a substantial improvement in wear performance and retention of hardness through to vir-tually no change in wear performance and substantial falls in hardness. Fracture toughness, however, increased markedly in all alloys with increasing austenitizing temperature. Tempering treatments in the range 400 °C to 600 °C, following hardening at the austenitizing temperature used commonly in industrial practice for each alloy, produced significant changes in both hard-ness and wear performance, but negligible changes in fracture toughness. Most importantly, the data showed that selection of the correct temperature for subcritical heat treatment to reduce the retained austenite content for applications involving repeated impact loading is critical if abrasion resistance is not to suffer.

The influence of heat treatment on the high-stress abrasion resistance and fracture toughness of alloy white cast irons

A series of heat treatments was employed to vary the microstructure of four commercially important alloy white cast irons, the wear resistance of which was then assessed by the ASTM jaw-crusher gouging abrasion test Compared with the as-cast condition, standard austenitizing treatments produced a substantial increase in hardness, a marked decrease in the retained aus-tenite content in the matrix, and, in general, a significant improvement in gouging abrasion resistance The gouging abrasion resistance tended to decline with increasing austenitizing tem-perature, although the changes in hardness and retained austenite content varied, depending on alloy composition Subcritical heat treatment at 500 ° following hardening reduced the retained austenite content to values less than 10 pct, and in three of the alloys it caused a significant fall in both hardness and gouging abrasion resistance The net result of the heat treatments was the development of optimal gouging abrasion resistance at intermediate levels of retained aus-tenite The differing responses of the alloys to both high-temperature austenitizing treatments and to subcritical heat treatments at 500 ° were related to the effects of the differing carbon and alloying-element concentrations on changes in theMs temperature and secondary carbide precipitation

B. K. Arnold

Papers

The influence of heat treatment on the high-stress abrasion resistance and fracture toughness of alloy white cast irons

The effect of heat treatment on the gouging abrasion resistance of alloy white cast irons

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