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This paper studies the influence of variables such as holding temperatures and times during austempering of High Chromium White Cast Iron (HCWCI), with the following chemical composition: Cr 25 %, C 3 %, Si 0.47 %, Mn 0.74 % and Mo 1.02 %. The aim of the austempering was to modify the percentage of retained austenite and its correlation to abrasive wear resistance under different conditions.Microhardness tests, SEM-EDS and XRD were performed to determine mechanical properties, chemical composition, and type of carbides and microstructures present, respectively. The tests complied with the ASTM G-65 standard. Results showed that the best performance against abrasion was achieved for austempering at 450 ºC with holding time of 6 hours., Este trabajo estudia la influencia de variables tales como tiempo y temperatura de sostenimiento durante el austemperado de una fundición blanca al alto cromo con la siguiente composición: Cr, 25 %; C, 3 %; Si, 0.47 %; Mn, 0.74 %, y Mo, 1.02 %. El objetivo del austemperado fue modificar el porcentaje de austenita retenida, y correlacionarlo con la resistencia al desgaste abrasivo bajo diferentes condiciones; los ensayos fueron realizados según los lineamientos de la norma ASTM G65. Las técnicas de microdureza MEB-EDS y DRX fueron realizadas para determinar las propiedades mecánicas, composición química, tipo de carburos y microestructuras presentes, respectivamente. Los resultados mostraron que la mejor resistencia a la abrasión fue alcanzada a una temperatura de austemperado de 450 ºC y a 6 horas de permanencia.

This paper studies the influence of variables such as holding temperatures and times during austempering of High Chromium White Cast Iron (HCWCI), with the following chemical composition: Cr 25 %, C 3 %, Si 0.47 %, Mn 0.74 % and Mo 1.02 %. The aim of the austempering was to modify the percentage of retained austenite and its correlation to abrasive wear resistance under different conditions.Microhardness tests, SEM-EDS and XRD were performed to determine mechanical properties, chemical composition, and type of carbides and microstructures present, respectively. The tests complied with the ASTM G-65 standard. Results showed that the best performance against abrasion was achieved for austempering at 450 ºC with holding time of 6 hours., Este trabajo estudia la influencia de variables tales como tiempo y temperatura de sostenimiento durante el austemperado de una fundición blanca al alto cromo con la siguiente composición: Cr, 25 %; C, 3 %; Si, 0.47 %; Mn, 0.74 %, y Mo, 1.02 %. El objetivo del austemperado fue modificar el porcentaje de austenita retenida, y correlacionarlo con la resistencia al desgaste abrasivo bajo diferentes condiciones; los ensayos fueron realizados según los lineamientos de la norma ASTM G65. Las técnicas de microdureza MEB-EDS y DRX fueron realizadas para determinar las propiedades mecánicas, composición química, tipo de carburos y microestructuras presentes, respectivamente. Los resultados mostraron que la mejor resistencia a la abrasión fue alcanzada a una temperatura de austemperado de 450 ºC y a 6 horas de permanencia.

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 CO2 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.

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 CO2 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.

The properties of the high-chromium white iron (HCWI) hardfaced materials, such as hardness, toughness and wear resistance, are affected by the morphology of their reinforcing phase, the Cr-carbides. In this work, the influence of the 1) welding parameters, 2) welding procedures and 3) chemical composition on the near-surface Cr-carbides morphology is presented. Additionally, the effects of the nucleo C® formula (Castolin Eutectic Ltd.) of unknown composition are evaluated. The hardfaced coatings are deposited by using the submerged metal arc welding (SMAW) process. The obtained near-surface structures are observed with scanning electron microscope with energy dispersive system (SEM-EDS). The structure morphological parameters are quantitatively determined by use of the ImageJ software. In the single-layer HCWI hardfaced coatings, larger heat input per unit length (≈ 4.1 kJ/mm) is leading to a formation of the hypoeutectic structures. An approximately two times lower heat input (≈ 1.8 kJ/mm) stimulates the solidification of the near-eutectic structures with presence of spheroidized eutectic and primary Cr-carbides (the Nucleo C effect). The double-layer coatings deposited with the ≈ 1.8 kJ/mm possess the hypereutectic structures with blade-like primary and needle-like eutectic carbides (the absence of the Nucleo C effect). The lower heat input (≈ 1.4 kJ/mm) and increase of the chromium and carbon content result in a formation of the hypereutectic structures with presence of the primary rod-like Cr-carbides embedded in the eutectic matrix with coarser and irregular eutectic Cr-carbides. The influence of the nucleo C® formula on the Cr-carbides morphology is more pronounced in the single-layer HCWI hardfaced coatings than in the double-layer coatings.

info:eu-repo/semantics/published

info:eu-repo/semantics/published

This report summarizes the results obtained in a study of metastable alloys produced by ultra-rapid quenching from the melt (splat cooling). The crystal structures of new metastable phases were determined by X-ray powder diffractometry; the energy dispersive diffraction technique originally intended for use in this work was evaluated and improved but found to be less powerful for the present purpose than angular dispersive diffractometry. Results in six main areas are listed: (1) B-metal alloys, including the Sn-Tl, Hg-In, Hg-Tl and Pb-Sn systems and Ga phases with In and Sn; (2) Ge alloy phases with Fe, especially a vacancy-stabilized CsCl type Ge-Fe phase connecting with six-coordinated metastable Ge(Fe); (3) A review of the splat cooling process; (4) Structures of the equilibrium phases AuPb3, Cr5Si3Cx, and 5 ternary M phases; (5) Use of energy dispersive counters for X-ray diffraction work; (6) Structures of metastable alloys at high pressures. (Modified author abstract)