Fatigue life enhancement of al-alloy 7075 under combined laser and hydrofluoric acid interaction

Abstract EN

Laser shock peening (LSP) is a technical method for generation the compressive residual stress.

LSP has been shown to greatly improve fatigue strength and lifetime.

A study of fatigue under a constant repeating bending stress has been conducted on AL-alloy 7075 alloy at a stress ratio (R= -1) and room temperature using laser peening technique with overlay hydrofluoric acid (HF) as a confinement acid layer and as a media to increase the penetration of laser pulses.

Two groups of test have been considered.

The first group (15 specimens) was examined under unpeened situation.

The second group (15 specimens) was examined under acid laser peening (ACLP).

All mentioned groups were tested to generate the S - N curve.

hydrofluoric acid (HF) coating was used as a new technique to improve the properties of the AL-alloy 7075.

The experimental data showed that the use of (HF) acid, as a coating material, largely increased the compressive residual stress at the surface.

The results provided a substantial improvement in fatigue life improvement factor reaching to 80% for this new coating.