Effects of Microstructure in the Carburized Layer on the Fatigue Strength of Vacuum Carburized Cr-Mo Steel (SCM 420)

Okamoto, Koji; Tominaga, Masatake; Ono, Hyoe; Nishiyama, Yukio

doi:10.2320/jinstmet1952.46.8_827

Cited by 5 publications

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“…For the CTC process, the average retained austenite content is 24.4%, which confirms the observations and results presented in Section 3.2. This austenite content, apart from reducing the mechanical properties, also has a negative effect on fatigue strength [32,34,[37][38][39][40][41]. Moreover, the influence of the phase structure, including the content of retained austenite discussed above, is important from the point of view of stress distribution and uniformity (Figure 6).…”

Section: Xrd Resultsmentioning

confidence: 99%

Minimizing Deformations in High-Temperature Vacuum Carburizing

Atraszkiewicz,

Dybowski

2023

Materials

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This article presents the results of a study on reducing deformations resulting from high-temperature vacuum carburizing and post-carburizing heat treatment. The idea was to increase the strength of steel at elevated temperatures by pre-carburizing at heat-up to the process temperature (SC—stage carburizing). It has been shown that the use of carburizing in stages from a lower temperature to the target temperature, compared to traditional vacuum carburizing at a constant temperature (Constant-Temperature Carburizing—CTC), has a significant impact on the chemical and phase composition of the technological layer, surface after the process and, consequently, on its mechanical properties. It was shown that the retained austenite content after stage carburizing was reduced by approximately 45%, as was the thickness of the gear teeth measured at the pitch diameter. Additionally, uniform stress distribution was demonstrated for the SC process. Carbon saturation of austenite increases the yield strength, and therefore the dimensional stability of steel heat-treated at elevated temperatures also improves, which effectively permits high-temperature treatment of critical steel parts such as, for example, gear wheels, for which high dimensional accuracy is required.

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Section: Xrd Resultsmentioning

confidence: 99%

Minimizing Deformations in High-Temperature Vacuum Carburizing

Atraszkiewicz,

Dybowski

2023

Materials

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Microstructures of SUS304 Stainless Steel after Long-Term Service in Vacuum Carburizing Quenching

Luan

Okuyama

Koizumi

2023

J. Japan Inst. Metals and Materials

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The microstructural changes and crack propagation in the carburized layer of SUS304 stainless steel due to repeated vacuum carburizing quenching as a heat treatment basket were investigated in this paper. As a result, beneath a graphite scale formed on the outermost surface, it was revealed that there were three types of carburized layers with different morphologies: M 7 C 3 layer, M 7 C 3 /M 23 C 6 mixed layer, and M 23 C 6 layer (M = Cr, Mn, Fe). In addition, the surface was found to be uneven due to the occurrence of metal dusting. Besides, repeated heating and quenching caused the formation of voids in carbides and matrix in the carburized layer, and micro cracks appeared in the surrounding areas. Under the loading stress during vacuum carburizing quenching, these voids, micro cracks, and the uneven surface are considered to be the initial points for cracking.

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Influence of Nb Addition on Microstructure and Creep Property of Heat-Resistant Cast Steel in Vacuum Carburizing and Quenching

et al. 2022

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The relation between microstructure and creep property of austenitic heat-resistant cast steels with and without Nb addition under the condition of repeated vacuum carburizing and quenching was investigated. Cr-carbide scale is formed on the sample surface by a carburizing reaction, resulting in the depletion of Cr in the matrix adjacent to the scale. A carburized layer consisting of various fine carbides is observed below the Cr-depleted layer, and the carburized layer depth is suppressed by Nb addition. When process of vacuum carburizing and quenching is repeated, formation of voids caused by heating and rapid cooling is more remarkable in primary Cr carbides than in primary Nb carbides. As the carburized layer depth increases, creep rupture time of both cast steels shifts to the shorter time side; however, Nb addition is effective for extending creep rupture time at 1303 K.

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Effects of Microstructure in the Carburized Layer on the Fatigue Strength of Vacuum Carburized Cr-Mo Steel (SCM 420)

Cited by 5 publications

References 0 publications

Minimizing Deformations in High-Temperature Vacuum Carburizing

Minimizing Deformations in High-Temperature Vacuum Carburizing

Microstructures of SUS304 Stainless Steel after Long-Term Service in Vacuum Carburizing Quenching

Influence of Nb Addition on Microstructure and Creep Property of Heat-Resistant Cast Steel in Vacuum Carburizing and Quenching

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