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Hann, SK; Gates, J.D.

doi:10.1023/a:1018544204267

Cited by 60 publications

(41 citation statements)

References 19 publications

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“…In order to obtain a better wear performance, the high chromium white cast irons should present a martensitic structure, because the martensitic formation, compared to the austenitic, minimizes cracking and removal during wear. While it was considered that the presence of residual austenite in the microstructure causes volumetric expansion which may also lead to microcracks because of the developed stresses, some investigations determined that a certain percentage of retained austenite could improve the abrasion resistance, due to its work-hardening properties [3,4], ductility and thermodynamic metastability at room temperature [5]. According to Liu et al [6] the best abrasion resistance is obtained when the content of retained austenite is higher than 20%.…”

Section: Introductionmentioning

confidence: 99%

Mejoramiento de la resistencia al desgaste abrasivo de la fundición al alto cromo ASTM A-532 a través de ciclos de tratamiento térmico

2016

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High-Chromium White Cast Iron is a material highly used in mining and drilling shafts for oil extraction, due to its high wear resistance. However, because of the austenitic matrix found in the as-cast state, an adequate heat treatment cycle is necessary. This paper studies the effects of different cooling media after a destabilization treatment on the microstructure, hardening and abrasion resistance behaviors of a hypoeutectic high chromium white cast iron. The results show that although air cooling followed by immersion in CO 2 can effectively reduce the retained austenite, this is not enough to transform completely the retained austenite into martensite. The low retained austenite percentages improve bulk hardness, but they decrease the abrasion resistance of the high chromium cast iron. The best combination of hardness and wear resistance was found in the samples cooled in air, due to the percentage of retained austenite and a moderate precipitation of chromium carbide.Keywords: High chromium white cast iron, HCWCI, White cast iron, Chromium carbides, Hardness, Wear testing, Austenite, Martensite. Improvement of abrasive wear resistance of the high chromium cast iron ASTM A-532 through thermal treatment cycles ResumenLas fundiciones blancas de hierro al alto cromo son muy usadas en la minería y en la perforación de pozos petroleros, debido a su alta resistencia al desgaste; sin embargo, debido a que en el estado de colada su microestructura es austenítica, es necesario someterlas a un adecuado ciclo de tratamiento térmico. Este trabajo estudia los efectos de los diferentes medios de enfriamiento después de un tratamiento de desestabilización de la microestructura y, por ende, el efecto del grado de endurecimiento sobre el comportamiento a la abrasión de una fundición blanca al alto cromo hipoeutéctica. Los resultados muestran que a pesar de que el enfriamiento al aire, seguido por inmersión en CO 2 , puede reducir eficazmente la austenita retenida, esto no es suficiente para transformarla completamente en martensita. El bajo porcentaje de austenita retenida incrementa la dureza del material, pero disminuye la resistencia a la abrasión de las fundiciones al alto cromo. La mejor combinación de dureza y resistencia al desgaste se encontró en las muestras enfriadas al aire, debido al porcentaje de austenita retenida y a una moderada precipitación de carburos de cromo.Palabras clave: HCWCI, Fundiciones blancas de hierro, Fundición al alto cromo, Carburos de cromo, Austenita, Martensita. ResumoAs fundições brancas de ferro ao alto cromo são muito usadas na mineração e na perfuração de poços petroleiros, devido a sua alta resistência ao desgaste; porém, devido a que no estado de lingotamento sua microestrutura é austenítica, é necessário submetê-las a um adequado ciclo de tratamento térmico. Este trabalho estuda os efeitos dos diferentes meios de resfriamento depois de um tratamento de desestabilização da microestrutura e, consequentemente, o efeito do grau de endurecimento sobre o comportamento à abrasão ...

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Section: Introductionmentioning

confidence: 99%

Mejoramiento de la resistencia al desgaste abrasivo de la fundición al alto cromo ASTM A-532 a través de ciclos de tratamiento térmico

2016

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“…For all Cr irons, wear resistance, and mechanical properties in general, depend on the type, morphology and distribution of carbides, and on nature of the matrix structure. [4][5][6][7][8][9] The as-cast microstructure of the 25-30 % Cr irons consists of primary austenite dendrites, eutectic austenite (partially transformed to martensite) and interdendritic eutectic M 7 C 3 carbide.…”

Section: Introductionmentioning

confidence: 99%

“…Improved service performance can be obtained by heat treatments and additional alloying to provide harder, more wear resistant martensitic matrix structures or to obtain austenitic matrices with improved crack propagation resistance. 2,4,[6][7][8] Conventional heat treatment involves heating castings to and holding at 950-1 050°C, followed by air cooling and tempering. The holding period is called "destabilisation", since it allows carbon and chromium in the austenite matrix to come out of solution as precipitates of secondary carbide.…”

Section: Introductionmentioning

confidence: 99%

A Microstructural Study of Destabilised 30wt%Cr-2.3wt%C High Chromium Cast Iron

2004

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An as-cast 30wt%Cr-2.3wt%C cast iron was destabilised in the temperature range of 900-1 100°C for times of 2-8 h, followed by air cooling to room temperature. The resultant microstructures were examined using light microscopy (LM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Volume fractions of secondary carbide within the martensite matrix and of M 23 C 6 in eutectic carbides were determined. Vickers macrohardness and Vickers microhardness of the dendritic regions were also measured. It was found that morphologies of secondary carbide were cube, plate-like shape or discrete-rod. A duplex core-shell structure was found in the eutectic carbides after destabilisation. It consists of M 7 C 3 as a core surrounding by M 23 C 6 , while the secondary carbide in these alloys was identified as M 23 C 6 . Higher destabilisation temperatures resulted in coarser secondary carbides with comparable volume fraction, but less in counts per area. The volume fraction of M 23 C 6 within the duplex structure was also increased when increasing destabilisation temperature and time. The results from hardness measurements revealed that the overall macrohardness of the iron was increased with increasing the destabilisation temperature up to about 770 HV (30 kgf/15 s) at 1 025°C, whereas the microhardness of the dendritic regions reached the maximum value of 800 HV (100 gf/15 s) at about 1 025°C.

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“…Due to its carbon percentage, HCWCI reports liquidus, solidus and eutectic temperatures different from those presented in the unalloyed white cast irons (1290, 1260 and 1270 ºC respectively) [13,14]. However, as the carbon content dissolves in the austenite, and the tendency of eutectoid transformation increases, these temperatures of phase transformation tend to decrease due to the reduction of austenite stability in the transformation zone (Fig.…”

Section: Results and Analysismentioning

confidence: 89%