Abstract
This paper presents the results of an experiment to investigate the high cycle fatigue properties of the ultra-high strength steel TM210A. A constant amplitude rotating bending fatigue experiment was performed at room temperature at stress ratio R = −1. In order to evaluate the notch effect, the fatigue experiment was carried out upon two sets of specimens, smooth and notched, respectively. In the experiment, the rotating bending fatigue life was tested using the group method, and the rotating bending fatigue limit was tested using the staircase method at 1 × 107 cycles. A double weighted least square method was then used to fit the stress-life (S–N) curve. The S–N curves of the two sets of specimens were obtained and the morphologies of the fractures of the two sets of specimens were observed with scanning electron microscopy (SEM). The results showed that the fatigue limit of the smooth specimen for rotating bending fatigue was 615 MPa; the ratio of the fatigue limit to tensile strength was 0.29, and the cracks initiated at the surface of the smooth specimen; while the fatigue limit of the notched specimen for rotating bending fatigue was 363 MPa, and the cracks initiated at the edge of the notch. The fatigue notch sensitivity index of the ultra-high strength maraging steel TM210A was 0.69.
Highlights
In order to meet the needs of high weight loads, high-transmission ratio, long life, weight and volume limits of important bearing units such as the leading edge flaps of a certain aircraft, material must have performance qualities such as high strength, high plasticity (δ5 ≥ 7.5%, ψ ≥ 45%), high toughness, high hardness (HRC ≥ 51) and high fatigue strength (σ−1 ≥ 680 MPa (3 × 106 ))
In order to investigate the fatigue strength and the facture mode of the ultra-high strength maraging steel TM210A, rotating bending fatigue tests were carried out using a smooth specimen and a notched specimen
The mean fatigue S–N curve and the mean fatigue limit of the smooth specimen and the notched specimen of the ultra-high strength maraging steel TM210Awere obtained in experiments
Summary
In order to meet the needs of high weight loads, high-transmission ratio, long life, weight and volume limits of important bearing units such as the leading edge flaps of a certain aircraft, material must have performance qualities such as high strength (σb ≥ 2058 MPa, σ0.2 ≥ 1960 MPa), high plasticity (δ5 ≥ 7.5%, ψ ≥ 45%), high toughness (αk ≥ 39.2 J/cm , KIC ≥ 62 MPa·m1/2 ), high hardness (HRC ≥ 51) and high fatigue strength (σ−1 ≥ 680 MPa (3 × 106 )). In the past many materials have been unable to meet these requirements. TM210A has been developed based on the design of the 18Ni maraging steel. The maraging steels are based on the iron-nickel-cobalt-molybdenum system that has emerged as an outstanding family of materials with exceptional combinations of characteristics. They are applied particulary in automotive, aerospace, nuclear, gear, bearing and other industries [1]. These grades generally contain 18 wt %
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