Influence of Chemical Carbon Microheterogeneity on Fatigue Crack Growth Parameters in Railway Wheel Steel

Abstract:

Actuality. The accumulation of damage due to fatigue, plastic deformation, and wear significantly reduces the service life of railway rolled metal products. The development of a fatigue crack to its critical length (main cracks) leads to failure at stress levels much lower than the material's strength limit. In industrial-grade steels, there may be chemical micro-inhomogeneity of the main element—carbon. Objective of the study: To determine the effect of chemical micro-inhomogeneity (carbon content variation of 0.02%) on fatigue failure characteristics (crack growth rate, threshold stress intensity factor, fatigue life, and critical defect size) of railway wheel steels of grades ER7 and ER8 according to EN 13262. Results. Segments of the fatigue crack growth rate (FCGR) diagram were constructed to characterize the development of fatigue cracks. The crack growth rate on the second linear section of the diagram and the critical value of the stress intensity factor at which failure occurs were determined. It was found that on the linear portion, which describes the crack growth process, the indicator values vary slightly (up to 10%), indicating that the crack growth rate differs minimally between these steels. Fatigue life—the number of loading cycles until failure—was also determined, and the critical size of the fatigue crack was calculated. A carbon content fluctuation within 0.02% by mass leads to a reduction in fatigue life by approximately 10% for ER7 steel and about 20% for ER8 steel, and a reduction in the critical crack size by around 8% for ER7 and 18% for ER8. Conclusion. Chemical micro-inhomogeneity with carbon content variation in the range of 0.02% in ER7 and ER8 railway wheel steels leads to a decrease in fatigue life (as determined from specimens with cracks) and in the critical size of the fatigue crack (up to 20%). However, it has only a minor effect (about 10%) on the stable fatigue crack growth rate.

• Periodical: Defect and Diffusion Forum (Volume 448)
• Pages: 77-82
• DOI: https://doi.org/10.4028/p-ty05DP
• Online since: March 2026
• Authors: Oleksandr I. Babachenko, Ganna A. Kononenko*, Rostislav V. Podolskyi, Olena A. Safronova, Oleksandr L. Safronov
• Keywords: Chemical Composition, Fatigue Crack Growth, Fatigue Failure, Mechanical Properties, Railway Wheel

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