Analysis of Fatigue Crack Propagation in AISI 4140 Steel with Multi-Austempering Treatment

Abstract:

This study examines the fatigue crack propagation behaviour of AISI 4140 steel subjected to multi-austempering heat treatments. Tensile test and fatigue crack propagation (FCP) specimens were prepared in accordance with ASTM E8 and ASTM E647, respectively. Multi-austempering was carried out by heating the specimen to an austenite temperature for 10 min using an induction heating coil. The specimen was then immersed in a salt bath for each isothermal transformation time of 60 min at three austempering temperature levels from 312°C to 412°C with a temperature increase of 50°C. Tensile and fatigue crack growth tests were performed on both annealed and multi-austempered specimens. It is observed that the multi-austempering heat treatment significantly improves the tensile properties and the FCP properties of AISI 4140 steel. Microstructural observations indicate that the bainitic phase and the retained austenite increase the tensile strength and reduce the fatigue crack propagation rate (da/dN). It is found that the bainitic structures are an effective barrier in reducing fatigue crack propagation as the fatigue loading cycle increases

• Periodical: Materials Science Forum (Volume 1138)
• Pages: 13-19
• DOI: https://doi.org/10.4028/p-C7nuYg
• Online since: December 2024
• Authors: Sugiyanto Sugiyanto, David Tarade Saragih, Krisna Ahmad Khan, Samro Matanari, Slamet Sumardi, Harnowo Supriadi, Mohammad Badaruddin*
• Keywords: AISI 4140 Steel, Bainitic Structure, Fatigue Crack, Multi-Austempering, Retained Austenite

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