HTM Journal of Heat Treatment and Materials

Published by De Gruyter

Volume 77 Issue 1

February 2022

Issue of HTM Journal of Heat Treatment and Materials

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Contents
Journal Overview

Publicly Available February 15, 2022

Page range: 1-2

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Open Access February 15, 2022

Low Temperature Carburizing of Stainless Steels and the Development of Carbon Expanded Austenite*

K. V. Werner, H. L. Che, M. K. Lei, T. L. Christiansen, M. A. J. Somers

Page range: 3-15

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Abstract

Low-temperature carburizing dramatically enhances the inherently low wear resistance of austenitic stainless steels due to the formation of a carbon-supersaturated solid solution, i.e. expanded austenite. The formation of expanded austenite from low-temperature carburizing has been intensively investigated. However, the influence of chemical composition of the stainless steel on the carburizing response has not received the same interest. This contribution addresses the effect of the chemical composition on low-temperature carburizing in terms of carbon solubility, decomposition of expanded austenite upon exceeding the solubility limit and the elasto-plastic accommodation of the carbon-induced lattice expansion. The results demonstrate that the carbon solubility increases with an increasing Cr-equivalent and that higher Cr- and Ni-equivalents favor the formation of Cr-based M 7 C 3 over Fe-based Hägg (M 5 C 2 ) carbide.

December 24, 2021

Dimensional Stability of Low Temperature Surface Hardened Stainless Steel Components*

A. Bauer, K. Schreiner

Page range: 16-28

Abstract

Stainless steels are commonly used for high precision components, which often are exposed to corrosive media. However, their inferior tribological behaviour restrict the use of these materials in many technical applications. Thermochemical surface hardening is one way to overcome these weaknesses. Solution nitriding in the austenitic range above 1000 °C is mainly used for hardening martensitic and ferritic stainless grades. In austenitic and duplex stainless grades, however, the hardening effect is limited. Additionally, the high process temperatures combined with a necessary rapid cooling may lead to non-desired dimensional changes. Low temperature surface hardening processing below 500 °C here offers interesting alternatives for increasing the wear properties, while maintaining the corrosion resistance. This paper demonstrates the influence of high and low process temperatures of thermochemical surface hardening treatments on the tight dimensional tolerances of a rotationally symmetrical precision component made from cold worked AISI 304. Based on these results, current and new industrial applications, which benefit from low temperature surface hardening, will be discussed.

February 15, 2022

Interrelation between Microstructure and Residual Stresses for Low-Pressure Carburizing of Steel AISI 5120 under Defined Process Parameter Variation

M. G. Zuern, O. B. Tapar, P. Ho, J. Epp, J. Gibmeier

Page range: 29-52

Abstract

Low-pressure carburizing (LPC) is a recipe-controlled process for surface layer hardening. These recipes are mainly based on experience and contain the process parameters used to achieve the desired hardening result. The process parameters influence the chemical gradients which have set in the boundary layer, the local microstructure and the depth distribution of the process-induced residual stresses. Within the scope of this work, a systematic parameter study and advanced characterization was carried out to quantify the influence of these process parameters on the resulting material state. The varied parameters include the carburizing temperature, the hardening temperature, the quenching rate as well as the number of repetitions and durations of the carburizing cycles’ steps. The results obtained should help to extend the fundamental process understanding of the LPC process. The analyses showed that the retained austenite content and its depth profile change significantly for certain process parameter variations, reaching contents of up to 45 vol% in the near-surface region. The differences regarding the residual stress states of the case-hardened samples can first and foremost be related to the formation of varying depth distributions of the retained austenite.

February 15, 2022

Investigations on the Hardness and Grain Size of Gears made out of Ultra-Clean Gear Steels after Case-Hardening

D. Fuchs, E. Fiederling, T. Tobie, K. Stahl

Page range: 53-69

Abstract

Kurzfassung Härte und Korngröße von Zahnrädern aus hochreinen Zahnradstählen nach Einsatzhärtung und Kugelstrahlen wurden im Rahmen eines Forschungsprojekts untersucht, dessen Schwerpunkt auf der Bestimmung der Zahnfußtragfähigkeit von einsatzgehärteten, kugelgestrahlten Zahnrädern lag. Die häufigste Versagensart bei diesen hochfesten Zahnrädern ist der Zahnfußbruch, der durch eine Rissinitiierung unterhalb der Oberfläche an einem nicht-metallischen Einschluss verursacht wird (Bruchlinsenversagen, im Englischen: Fisheye failure). Neben solchen Einschlüssen sind auch die Härte und die Abschreckkorngröße dafür bekannt, dass sie einen erheblichen Einfluss auf die Tragfähigkeit eines Zahnrades haben. Um sicherzustellen, dass in diesem Forschungsprojekt ausschließlich der Einfluss von nicht-metallischen Einschlüssen untersucht wird, mussten mögliche Quereinflüsse ausgeschlossen, minimiert oder zumindest bekannt sein. Nach einem ungeeigneten Einsatzhärtungsprozess erreichen Zahnräder jedoch nicht die härtebezogenen Spezifikationen, oder Zahnräder aus Zahnradstählen mit hoher Feinkornstabilität können Mengen an gröberen Körnern enthalten. Daher wurden Einsatzhärtungsparameter abgeleitet und überprüft, ob sie zu den für einsatzgehärtete Zahnradstähle geforderten Korngrößen- und Härtespezifikationen nach ISO 6336 führen. Weiterhin wurde untersucht, wie sich ein reduzierter Aluminiumgehalt bei resultierenden höheren Reinheitsgrad, d. h. kompensiert durch eine Nioblegierung zur Erhaltung der Feinkornstabilität, auf die Korngröße nach dem Einsatzhärten auswirkt.

February 15, 2022

Gearbox Production Using Distortion Controlled Inductive Fixture Hardening*

S. Knauf, K. Buchner, R. Jenne

Page range: 70-85

Abstract

Fixture-hardening, also known as quench-press hardening, is a widespread process mainly for the automotive industry. This paper introduces a new inductive hardening and tempering process that combines the well-known advantages of induction heating and hardening with the advantages of a fixture hardening process to obtain highly precise workpieces with enormously reduced or even without rework. The main component is a new hardening machine with implemented fixture hardening assembly and integrated induction coil, all in a protective gas atmosphere. Induction as electrical energy source can be used for heating up workpieces prior to fixture hardening and for tempering, which allows to simultaneously draw out the calibration mandrel without any abrasive wear on its surface. In certain applications, an expanding mandrel can be used in order to relieve the workpiece.

Impressum/Imprint

February 15, 2022

Impressum/Imprint

Page range: 86-86

From and for Practice / Praxis-Informationen

February 15, 2022

AWT-Info / HTM 01-2022

Page range: A5-A17

February 15, 2022

HTM Praxis

Page range: A18-A36

About this journal

HTM is a bilingual (German-English) independently assessed and periodical standard publication that provides reports on all aspects of heat treatment and material technology in research and production. By publishing trend-setting contributions to research and practical experience reports, HTM helps in answering scientific questions as well as regarding investment decisions in the industry. All articles are subject to thorough, independent peer review.
HTM is the official organ of AWT – the Association of Heat Treatment and Materials Technology.

Volume 77 Issue 1

Issue of HTM Journal of Heat Treatment and Materials

Contents

Low Temperature Carburizing of Stainless Steels and the Development of Carbon Expanded Austenite*

Abstract

Dimensional Stability of Low Temperature Surface Hardened Stainless Steel Components*

Abstract

Interrelation between Microstructure and Residual Stresses for Low-Pressure Carburizing of Steel AISI 5120 under Defined Process Parameter Variation

Abstract

Investigations on the Hardness and Grain Size of Gears made out of Ultra-Clean Gear Steels after Case-Hardening

Abstract

Gearbox Production Using Distortion Controlled Inductive Fixture Hardening*

Abstract

Impressum/Imprint

AWT-Info / HTM 01-2022

HTM Praxis