Carbo-Austempering™ - A New Wrinkle?

Hayrynen, Kathy L.; Brandenberg, Kristin; Keough, John R.

doi:10.4271/2002-01-1478

Cited by 22 publications

(27 citation statements)

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“…For gears only very limited information on heat treatments with bainitic transformation of the case is available. In the USA few suppliers are propagating carbo-austempering heat treatment for case hardening applications [1]. In the literature a combination of carburization and austempering is discussed with only scarce data on material and microstructure performance [2][3][4][5][6].…”

Section: Abstract/kurzfassungmentioning

confidence: 99%

“…Daher ist die Anwendung einer isothermischen Umwandelung in Bainit im Anschluss an die Aufkohlung von Zahnrädern heute nicht Stand der Technik und nur sehr begrenzte Informationen zu Wärmebehandlung und Tragfähigkeit so behandelter Zahnräder sind verfügbar. Ferner sind nur wenige Anwender bekannt [1]. In der gängigen Literatur ist die Verfahrenskombination ebenso eher selten anzutreffen und nur mit begrenztem Versuchsumfang belegt [2][3][4][5][6].…”

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CarboBain: Case Hardening by Carbo-Austempering–a short Introduction to Transformation Kinetics, Microstructure and Residual Stresses*

Steinbacher

Zoch

2017

HTM Journal of Heat Treatment and Materials

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Abstract/KurzfassungThe beneficial strength properties of bainitic microstructures have been perceived since several years. The transformation kinetics and different morphologies of bainite were analyzed scientifically in depth and with increasing understanding the application of bainite is focus now. But still, bainitic microstructures are mainly utilized with chemically homogeneous steels. An application of bainitic transformed carburized samples is rather rare up to now. Therefore highly stressed geared components today typically are carburized and martensitically hardened. The microstructure in the case is generally composed of martensite with finely dispersed retained austenite and/or carbides. For gear wheel application during the past 50 years research was focused on topics like microstructure optimization within the bounds of martensite with no more than 25 % of retained austenite. For gears only very limited information on heat treatments with bainitic transformation of the case is available. In the USA few suppliers are propagating carbo-austempering heat treatment for case hardening applications [1]. In the literature a combination of carburization and austempering is discussed with only scarce data on material and microstructure performance [2][3][4][5][6]. To close the gap a systematic approach was made in a public funded project, analyzing transformation kinetics, microstructure properties and mechanical performance of two typical case hardening steels in carburized state being bainitic transformed. The heat treatment method using case hardening by carburization and adjacent austempering, the transformation behaviour, microstructure development and mechanical properties will be discussed. achieve a comparable state of solution and distribution of carbon all samples in dilatometer were first austenitized at 940 °C for at least 10 min, then cooled to 840 °C and held for 15 min. Subsequently they were quenched with nitrogen gas at maximum cooling speed to RT for determination of martensite start temperature or quenched to isothermal holding temperature for transformation into bainite. After isothermal holding time had passed samples were cooled to RT and passed on to metallographic analysis. Heat treatment of samplesThe samples within the microstructure investigation were simple disc shaped samples of 30 × 30 × 8 in mm, which were carburized using a gas carburization process in a Solo202 Bell type furnace. Carburizing atmosphere is a RX-gas from methanol / nitrogen with propane. The samples were first heated up to a temperature of 850 °C held for 30 min at a Cp of 0.6 %. Then the furnace heated up to 940 °C at Cp 90 % soot limit and carburized at a Cp of 1.15 % until 80 % of CD (carburization depth) is reached. Adjacent the Cp is reduced to an appropriate level for designated surface carbon content. Finally the temperature is reduced to 850 °C at a Cp according to the designated surface carbon content and a holding step for 30 min. is performed before quenching. Samples were quenched after carburizati...

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Section: Abstract/kurzfassungmentioning

confidence: 99%

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CarboBain: Case Hardening by Carbo-Austempering–a short Introduction to Transformation Kinetics, Microstructure and Residual Stresses*

Steinbacher

Zoch

2017

HTM Journal of Heat Treatment and Materials

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“…Wear tests showed that the cast iron had properties comparable to those of the steel tested and that the wear resistance of ADI was increasing along with an increase in the nominal load. Hayrynen et al [12] found a significant reduction in the abrasive wear of ADI as compared with carbon steels with a hardness of 40HRC.…”

Section: Introductionmentioning

confidence: 99%

Comparative Studies on the Wear of ADI Alloy Cast Irons as Well as Selected Steels and Surface-Hardened Alloy Cast Steels in the Presence of Abrasive

Wieczorek¹

2017

Archives of Metallurgy and Materials

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The paper presents the results of wear tests obtained for 4 groups of materials: surface-hardened alloy steels and alloy cast steels for structural applications, hard-wearing surface-hardened alloy cast steels, and austempered alloy cast irons. The wear tests have been performed on a specially designed test rig that allows reproducing the real operating conditions of chain wheels, including the rolling and sliding form of contact between elements. The chain wheels subjected to tests were operated with the use of loose quartz abrasive. This study presents results of measurements of material parameters, micro-structure of a surface subject to wear, as well as the linear wear determined for the materials considered. Based on the results, the following was found: the best wear properties were obtained for surface-hardened alloy steels and wear surface; strengthening of the ADI surface took place -most probably as a result of transformation of austenite into martensite; the uniformity of the structure of the materials affects the surface wear process. The study also indicated a significant degree of graphite deformation in ADI characterized by the upper ausferritic structure and its oblique orientation in relation to the surface, which resulted in a facilitated degradation of the surface caused by the quartz abrasive.

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“…A number of authors, including Schissler et al [5], Owhadi et al [6], Hayrynen et al [7,8], Myszka and Wieczorek [9,10] confirmed a beneficial influence of the strain-induced transition on the wear properties of ADIs.…”

Section: Introductionmentioning

confidence: 99%

Abrasive Wear Properties of Fe-Based Alloys Designed for Mining Applications

Wieczorek¹,

Myszka²

2017

Archives of Metallurgy and Materials

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The purpose of this study was to determine experimentally the wear properties of 5 groups of iron-based alloys used in the mining and transport machines exposed to the action of a hard abrasive material. The groups of materials to be examined included austempered ductile irons (ADI), steels and cast steel designed for quenching and tempering and for surface hardening, hard-wearing hardened steels and structural steels. The wear tests were carried out on a disc-on-disc test rig. The test samples were examined under conditions of sliding mating, while the leading destructive process was microcutting of the surface with loose corundum grain. The loss of mass of the examined samples was measured as a parameter characterizing the wear. Base on it, other wear coefficients were determined, for example the volume loss, the intensity of wear and the wear rate. The volume loss values determined were presented as a function of the strength and the initial hardness. Based on the results obtained, it was found that the hardened steel and ADI had comparable wear properties, while the ADI surface was strengthened probably as a result of the transition of austenite into martensite and the impact of the deformation of the graphite contained in ADI on the abrasive wear of the surface.

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Carbo-Austempering™ - A New Wrinkle?

Cited by 22 publications

References 0 publications

CarboBain: Case Hardening by Carbo-Austempering–a short Introduction to Transformation Kinetics, Microstructure and Residual Stresses*

CarboBain: Case Hardening by Carbo-Austempering–a short Introduction to Transformation Kinetics, Microstructure and Residual Stresses*

Comparative Studies on the Wear of ADI Alloy Cast Irons as Well as Selected Steels and Surface-Hardened Alloy Cast Steels in the Presence of Abrasive

Abrasive Wear Properties of Fe-Based Alloys Designed for Mining Applications

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