High-Cycle Fatigue Properties of Ferritic-Pearlitic Medium-Carbon Forging Steels with Smooth and Notched Specimens

• Published in: Journal of materials engineering and performance Vol. 30; no. 3; pp. 2182 - 2192
• Main Authors: Zhao, Sixin, Yu, Dajiang, Hui, Weijun
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.03.2021
• Subjects: Characterization and Evaluation of Materials; Chemistry and Materials Science; Corrosion and Coatings; Engineering Design; Materials Science; Quality Control; Reliability; Safety and Risk; Tribology; high-cycle fatigue; medium-carbon forging steel; mechanical property; microstructure
• ISSN: 1059-9495; 1544-1024
• DOI: 10.1007/s11665-021-05533-6

High-cycle fatigue properties of two ferritic-pearlitic medium-carbon forging steels 30MnVS and 49MnVS with smooth and notched (stress concentration factor K t =2.1 and 3.9) specimens were studied by using rotating bending fatigue and fatigue crack growth (FCG) rate testing. Structural steels 40Cr and 30MnVS with quenched & tempered microstructures (40Cr-QT, 30MnVS-QT) were used for comparison. It was found that both fatigue strength and fatigue strength ratio at each K t of the as-forged 30MnVS steel (30MnVS-AF), which are comparable to those of 30MnVS-QT and 40Cr-QT, are notably higher than those of the as-forged 49MnVS steel (49MnVS-AF), and this difference tends to decrease with an increase in K t . However, 30MnVS-AF exhibits slightly higher fatigue notch sensitivity and FCG rate than 49MnVS-AF, and the steels with ferritic-pearlitic microstructure also have higher fatigue notch sensitivity than the steels with QT microstructure. A simple and practical method which incorporates simple microstructural parameters, and hardness is proposed to estimate the smooth fatigue strength ( σ w ) of ferritic-pearlitic forging steels, while notched fatigue strength can be expressed by a power function of K t with its coefficient equals to σ w , which can be further classified into two groups corresponding to forging steels with relatively lower and higher C contents, respectively.