The Effect of Temperature Distribution During Laser Heat Treatment of Gas-Nitrided 42CrMo4 Steel on the Microstructure and Mechanical Properties

A gas-nitrided layer was produced on the toughened 42CrMo4 low-alloy steel using the changeable nitriding potential in order to limit the thickness of a brittle ε zone. The microstructure consisted of the compound ε + (ε + γ’) zone and diffusion zone (nitric sorbite with γ’ precipitates). Such a lay...

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Main Authors: Dominika Panfil-Pryka, Michal Kulka, Natalia Makuch, Jerzy Michalski, Piotr Dziarski
Format: Article
Language:English
Published: MDPI AG 2020-08-01
Series:Coatings
Subjects:
Online Access:https://www.mdpi.com/2079-6412/10/9/824
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spelling doaj-70b4f6c57a0f447d85d65950fbb3af992020-11-25T03:51:26ZengMDPI AGCoatings2079-64122020-08-011082482410.3390/coatings10090824The Effect of Temperature Distribution During Laser Heat Treatment of Gas-Nitrided 42CrMo4 Steel on the Microstructure and Mechanical PropertiesDominika Panfil-Pryka0Michal Kulka1Natalia Makuch2Jerzy Michalski3Piotr Dziarski4Institute of Materials Science and Engineering, Poznan University of Technology, Pl. M.Sklodowskiej-Curie 5, 60-965 Poznan, PolandInstitute of Materials Science and Engineering, Poznan University of Technology, Pl. M.Sklodowskiej-Curie 5, 60-965 Poznan, PolandInstitute of Materials Science and Engineering, Poznan University of Technology, Pl. M.Sklodowskiej-Curie 5, 60-965 Poznan, PolandDepartment of Materials Engineering, Czestochowa University of Technology, Al. Armii Krajowej 19, 42-200 Częstochowa, PolandInstitute of Materials Science and Engineering, Poznan University of Technology, Pl. M.Sklodowskiej-Curie 5, 60-965 Poznan, PolandA gas-nitrided layer was produced on the toughened 42CrMo4 low-alloy steel using the changeable nitriding potential in order to limit the thickness of a brittle ε zone. The microstructure consisted of the compound ε + (ε + γ’) zone and diffusion zone (nitric sorbite with γ’ precipitates). Such a layer was subjected to laser heat treatment with or without remelting. The single laser tracks were formed using various laser beam powers (in the range of 0.234–0.624 kW) and scanning rates (in the range of 2.24–3.84 m·min<sup>−1</sup>) and the same laser beam diameter (2 mm). The microstructure of laser-modified nitrided layer usually consisted of re-melted zone (MZ) with coarse-grained nitric martensite Fe<sub>α’</sub> and possible ε precipitates, heat-affected zone (HAZ) with fine-grained nitric martensite Fe<sub>α’</sub> and γ’ precipitates and diffusion zone with nitric sorbite and γ’ precipitates. Sometimes, the compound zone was partially re-melted and an amount of iron nitrides remained in the MZ. Only one laser track was characterized by the different microstructure, consisting of the compound ε + (ε + γ’) zone, HAZ with fine-grained nitric martensite Fe<sub>α’</sub> and γ’ precipitates and diffusion zone with nitric sorbite and γ’ precipitates. This laser track was formed without visible effects of remelting. The effect of temperature distribution during laser heat treatment of gas-nitrided 42CrMo4 steel on the microstructure and mechanical properties was studied. The equations developed by Ashby and Esterling were used in order to determine the temperature distribution along the axis of each laser track. Taking into account the temperature profiles, it was possible to calculate the depths of MZ and HAZ. These predicted values were compared to those-measured based on the microstructure observations, obtaining good compatibility. The microstructure of the produced surface layers influenced the mechanical properties such as hardness and Young’s modulus. The hardness of MZ was higher than that of ε zone and lower than that of ε + γ’ zone when compared to nitrided layer. Whereas Young’s modulus of MZ was significantly higher than those characteristic of the compound zone in gas-nitrided layer (both ε and ε + γ’ zone) and similar to that of HAZ. The laser heat treatment (LHT) without remelting resulted in the similar hardness and slightly higher Young’s modulus of ε zone in comparison with the nitrided layer. Simultaneously, such a treatment of the nitrided layer did not influence the hardness and the Young’s modulus of ε + γ’ zone considerably. The hardness of HAZ was higher than that of MZ and that of the same area of diffusion zone in the nitrided layer because of the presence of fine-grained nitric martensite with γ’ precipitates after laser quenching.https://www.mdpi.com/2079-6412/10/9/824gas nitridingcompound zonelaser heat treatmenttemperature distributionmicrostructurehardness
collection DOAJ
language English
format Article
sources DOAJ
author Dominika Panfil-Pryka
Michal Kulka
Natalia Makuch
Jerzy Michalski
Piotr Dziarski
spellingShingle Dominika Panfil-Pryka
Michal Kulka
Natalia Makuch
Jerzy Michalski
Piotr Dziarski
The Effect of Temperature Distribution During Laser Heat Treatment of Gas-Nitrided 42CrMo4 Steel on the Microstructure and Mechanical Properties
Coatings
gas nitriding
compound zone
laser heat treatment
temperature distribution
microstructure
hardness
author_facet Dominika Panfil-Pryka
Michal Kulka
Natalia Makuch
Jerzy Michalski
Piotr Dziarski
author_sort Dominika Panfil-Pryka
title The Effect of Temperature Distribution During Laser Heat Treatment of Gas-Nitrided 42CrMo4 Steel on the Microstructure and Mechanical Properties
title_short The Effect of Temperature Distribution During Laser Heat Treatment of Gas-Nitrided 42CrMo4 Steel on the Microstructure and Mechanical Properties
title_full The Effect of Temperature Distribution During Laser Heat Treatment of Gas-Nitrided 42CrMo4 Steel on the Microstructure and Mechanical Properties
title_fullStr The Effect of Temperature Distribution During Laser Heat Treatment of Gas-Nitrided 42CrMo4 Steel on the Microstructure and Mechanical Properties
title_full_unstemmed The Effect of Temperature Distribution During Laser Heat Treatment of Gas-Nitrided 42CrMo4 Steel on the Microstructure and Mechanical Properties
title_sort effect of temperature distribution during laser heat treatment of gas-nitrided 42crmo4 steel on the microstructure and mechanical properties
publisher MDPI AG
series Coatings
issn 2079-6412
publishDate 2020-08-01
description A gas-nitrided layer was produced on the toughened 42CrMo4 low-alloy steel using the changeable nitriding potential in order to limit the thickness of a brittle ε zone. The microstructure consisted of the compound ε + (ε + γ’) zone and diffusion zone (nitric sorbite with γ’ precipitates). Such a layer was subjected to laser heat treatment with or without remelting. The single laser tracks were formed using various laser beam powers (in the range of 0.234–0.624 kW) and scanning rates (in the range of 2.24–3.84 m·min<sup>−1</sup>) and the same laser beam diameter (2 mm). The microstructure of laser-modified nitrided layer usually consisted of re-melted zone (MZ) with coarse-grained nitric martensite Fe<sub>α’</sub> and possible ε precipitates, heat-affected zone (HAZ) with fine-grained nitric martensite Fe<sub>α’</sub> and γ’ precipitates and diffusion zone with nitric sorbite and γ’ precipitates. Sometimes, the compound zone was partially re-melted and an amount of iron nitrides remained in the MZ. Only one laser track was characterized by the different microstructure, consisting of the compound ε + (ε + γ’) zone, HAZ with fine-grained nitric martensite Fe<sub>α’</sub> and γ’ precipitates and diffusion zone with nitric sorbite and γ’ precipitates. This laser track was formed without visible effects of remelting. The effect of temperature distribution during laser heat treatment of gas-nitrided 42CrMo4 steel on the microstructure and mechanical properties was studied. The equations developed by Ashby and Esterling were used in order to determine the temperature distribution along the axis of each laser track. Taking into account the temperature profiles, it was possible to calculate the depths of MZ and HAZ. These predicted values were compared to those-measured based on the microstructure observations, obtaining good compatibility. The microstructure of the produced surface layers influenced the mechanical properties such as hardness and Young’s modulus. The hardness of MZ was higher than that of ε zone and lower than that of ε + γ’ zone when compared to nitrided layer. Whereas Young’s modulus of MZ was significantly higher than those characteristic of the compound zone in gas-nitrided layer (both ε and ε + γ’ zone) and similar to that of HAZ. The laser heat treatment (LHT) without remelting resulted in the similar hardness and slightly higher Young’s modulus of ε zone in comparison with the nitrided layer. Simultaneously, such a treatment of the nitrided layer did not influence the hardness and the Young’s modulus of ε + γ’ zone considerably. The hardness of HAZ was higher than that of MZ and that of the same area of diffusion zone in the nitrided layer because of the presence of fine-grained nitric martensite with γ’ precipitates after laser quenching.
topic gas nitriding
compound zone
laser heat treatment
temperature distribution
microstructure
hardness
url https://www.mdpi.com/2079-6412/10/9/824
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