Phase Transformations During Heat Treatment of a CPM AISI M4 Steel
The phase transformations of Crucible Particle Metallurgy (CPM) American Iron and Steel Institute (AISI) M4 steel were studied during heat treatments using a CALPHAD-based method. The calculated results were compared with experimental observations. The optimum austenitizing temperature was determine...
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| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-07-01
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| Series: | Metals |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2075-4701/15/7/818 |
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| Summary: | The phase transformations of Crucible Particle Metallurgy (CPM) American Iron and Steel Institute (AISI) M4 steel were studied during heat treatments using a CALPHAD-based method. The calculated results were compared with experimental observations. The optimum austenitizing temperature was determined to be about 1120 °C using Thermo-Calc software (2024b). Air-cooling and quenching treatments led to the formation of martensite with a hardness of 63–65 Rockwell C (HRC). The annealing treatment promoted the formation of the equilibrium ferrite and carbide phases and resulted in a hardness of 24 HRC. These findings with regard to phases and microconstituents are in agreement with the predictions derived from a Thermo-Calc-calculated time–temperature–transformation diagram at 1120 °C. Additionally, the primary carbides, MC and M<sub>6</sub>C, which formed prior to the heat treatment and had a minor influence on the quenched hardness. In contrast, the tempering process primarily led to the formation of fine secondary M<sub>6</sub>C carbides, which hardened the tempered martensite to 57 HRC. The present work demonstrates the application of a CALPHAD-based methodology to the design and microstructural analysis of tool steels. |
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| ISSN: | 2075-4701 |