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Study the Microstructure and Mechanical Properties of High Chromium White Cast Iron (HCWCI) under Different Martempering Quenching Mediums.

Authors: Ali H. Ataiwi --- Zainab A. Betti
Journal: Engineering and Technology Journal مجلة الهندسة والتكنولوجيا ISSN: 16816900 24120758 Year: 2019 Volume: 37 Issue: 4part (A) Engineering Pages: 112-119
Publisher: University of Technology الجامعة التكنولوجية

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Abstract

This study aims to find the effect of hydroxide mixture as a quenchingmedium in martempering heat treatment on microstructure and mechanicalproperties of high chromium white cast iron. This mixture is cheaper and moreavailable than the ordinary nitrate mixture in Iraqi markets. High chromiumwhite cast iron is used in mining, crushing and cement plants as mill liners andit is subjected to extreme conditions of wear and impact that cause failure,reduction in life and raise the cost of repairing. Hence it is important toimprove its mechanical properties. In this study, two types of quenchingmediums were used:(50% NaOH: 50% KOH ) mixture and (50% NaNO3 + 50% KNO3) mixture. The specimens were austenitized at 950°C for 1 hr then thefirst group was quenched in nitrate mixture, and the other was quenched inhydroxide mixture both at about 350°C for (1/2, 2,4,6,8) hr. The results showedan increase in hardness and decrease in toughness for both mixtures, and thehigher hardness value was found for both of the mixtures at martemperingtemperature 350°C for 4hr quenching time.


Article
DESTABILIZATION HEAT TREATMENT EFFECT ON EROSIVE WEAR CHARACTERISTICS OF HIGH CHROMIUM WHITE CAST IRON

Authors: Ali H. Ataiwi --- Israa F. Yousif
Journal: KUFA JOURNAL OF ENGINEERING مجلة الكوفة الهندسية ISSN: 25230018 Year: 2018 Volume: 9 Issue: 2 Pages: 45-56
Publisher: University of Kufa جامعة الكوفة

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Abstract

In the present investigation, erosive wear property of high chromium white cast irons (HCWI) is reported. HCWI were destabilized at two different temperatures of 955oC and 1100°C, air cooling followed by tempering heat treatment at 400°C and 700°C at each destabilized temperature. Erosion damage was evaluated by the removed material mass at impact angle 45° and time of 10 Hours. The surface metal flow was observed. Surface morphology of each specimen was characterized with scanning electron microscopy (SEM). The effect of heat treatment on differences in wear features of specimens is discussed. Experiment showed that the erosion rate of specimen destabilized at 1100°C, air cooled followed by tempering at 400°C air cooling is the best than other treatments. The hardness of test surface by this treatment increased from the initial 57 to 58 HRC after 10 hour. It showed that austenite in the surface structure has been transformed to martensite , which hardened the surface. Similarly, work- hardening effect also occurred on specimen destabilized at 955°C, air cooled followed by tempering at 400oC, air cooling to make its surface hardness increased to 59 HRC. It was shown that HCWI series heat treated at 955°C and 1100°C and tempered at 400°C have a very good erosive wear resistance and they are expected to find wide application as wear-resistant materials.

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