Influence of Surface Enhancement by Low Plasticity Burnishing on the Corrosion Fatigue Performance of AA7075-T6

摘要

Conventional approaches to mitigate corrosion related failure mechanisms in aircraft usually involve isolation from the corrosive environment via protective coatings, alloy substitution, or modifications in design to reduce stresses. This paper describes an alternate approach employing surface enhancement by low plasticity burnishing (LPB) to eliminate or reduce the surface tensile stresses necessary for corrosion fatigue failure in AA7075-T6, without alteration of environment, material or component design. The restoration of fatigue performance by LPB processing of AA7075-T6 after severe pitting in salt fog was previously described. This paper describes benefits of introducing a deep compressive residual stress by LPB on fatigue strength after salt fog pitting and corrosion fatigue (under active corrosion) performance. Since LPB processing was performed in a conventional CNC machining center, it offers a cost effective and practical alternative to alloy substitution or component re-design as a means of improving the structural integrity of aging aircraft.