Effects of shot peening and artificial surface defects on fatigue properties of 50CrV4 steel

Abstract

Shot peening processes are commonly used for improving the fatigue properties of steels. Shot peening introduces a compressive residual stress field in the near surface of steel, which can reduce or stop the growth of fatigue cracks and improve fatigue properties. This study experimentally investigated the effect of shot peening on the fatigue properties of 50CrV4 steel alloys with different artificial surface defects. Drilling tools were used to introduce different artificial defects with root radii of 0.585 mm and 0.895 mm on the surface of unpeened samples. The shot peening was applied to the drilled and undrilled samples. Scanning electron microscopy (SEM) observations, micro-hardness and X-ray diffraction residual stress measurements were conducted to analyse the characteristics of the shot-peened and unpeened samples. The results show that the shot peening leads to the transformation of the retained austenite to martensite in the near-surface microstructure. The hardness rates of the surface and near surface both increase by 8% after the shot peening. The peened samples exhibit compressive residual stresses with a high degree of isotropy in the near surface. The fatigue properties of samples were experimentally evaluated by conducting 3-point bending tests. The results indicate that the shot peening improves the fatigue life of drilled and undrilled samples. For the defects with the root radius of 0.895 mm, the shot peening leads to a 500% improvement in the fatigue life compared to unpeened samples regardless of defect depth. For the defects with the root radius of 0.585 mm, the improvement in fatigue life is 40% for the defect depth of 0.2 mm compared to unpeened samples. The improvement increases to 60% and 200% by increasing the defect depths to 0.4 mm and 0.6 mm. The fatigue properties are linked to the changes in the features of defects mainly caused by the deformation hardening and compressive residual stress after shot peening.

Fatigue crack initiation and growth behavior within varying notch geometries in the low‐cycle fatigue regime for FV566 turbine blade material

“…An as‐received notch surface (with corrosion pitting) typically had a lower number of crack initiation events, possibly due to the onset of early initiation activity and growth behavior inhibiting later crack initiation due to shielding effects 1 . The shot peened notch surface typically had more crack initiation events than a polished or as‐received notch surface, especially at lower strain ranges due to the presence of pre‐existing cracks before testing (Figure 14), a feature seen in similar shot peened steels 6,23,24 …”

“…1 The shot peened notch surface typically had more crack initiation events than a polished or as-received notch surface, especially at lower strain ranges due to the presence of pre-existing cracks before testing (Figure 14), a feature seen in similar shot peened steels. 6,23,24 The number of crack initiation events observed on a shot peened U-notch surface made from FV448 with applied strain ranges between 0.6% and 0.9% 10 were almost doubled when assessed in the FV566 at the same strain range. This difference can be attributed to the method used to count the number of initiation events on the surface.…”

Determination of the optimal coverage for heavy-duty-axle gears in shot peening

“…The results are consistent with the findings expressed by other Refs. [48][49][50][51]. As depicted in Fig.…”

Microstructure Evolution and Wear Resistance Improvement of Ultrasonic Peened M50 Steel via Electromagnetic Shocking

“…For instance, it has been demonstrated that ultrasonic impact peening (UIP) technology plays a positive role in refining the grain size and increasing hardness and wear resistance. [8,9] In addition, the residual compressive stress was applied to the metal surface, which can heal the microcracks and holes during the cycle wear. [10] Yin et al [11,12] found that the ultrasonic shot peening (USP) can induce nanocrystalline structure on the surface, thereby improving the nanohardness and Young's modulus.…”