Application of shot peening treatments for increasing the durability of hot-forged components

Introduction

Hot forging is widely used in the automotive industry to manufacture components with enhanced mechanical properties. However, these components are often subjected to cyclic loads that can limit their service life through fatigue damage. Surface treatments such as shot peening are extensively used for their ability to induce compressive residual stresses and improve resistance to crack initiation and propagation.

Methods

This work investigates the effect of shot peening on the fatigue performance of hot-forged 6082-T6 aluminium alloy. The material was hot-forged at 525 °C in two press strokes. Shot peening was performed using different shot media, leading to Almen intensities ranging from 0.03 mm N to 0.30 mm A, while the peening time was kept constant at 240 s. Surface roughness, hardness, and residual stress were evaluated to assess the influence of the treatments on surface integrity. Axial fatigue tests were conducted in accordance with ISO 1099 under load control, using a 10 Hz sinusoidal waveform and a stress ratio of R = 0 to obtain the Wöhler curves.

Results and conclusions

Fatigue performance was found to depend strongly on the shot media employed. Fine spherical ceramic media increased the fatigue strength at 10⁷ cycles by up to 10% and extended the service life of tested specimens by one order of magnitude. In contrast, excessively hard and irregular ceramic particles proved to be detrimental to fatigue performance, reducing the fatigue limit at 10⁷ cycles by approximately 10%. These results are well supported by surface integrity measurements. Overall, the results demonstrate that the choice of shot media significantly influences the fatigue response and strengthening mechanisms of hot-forged 6082-T6 aluminum alloy, providing useful guidance for optimizing shot peening treatments.