Damage Tolerance Improvement of Ti-6-4 Fan Blades With Low Plasticity Burnishing

Abstract
Low plasticity burnishing (LPB) has been demonstrated to increase the damage tolerance of Ti- 6Al-4V fan blades by an order of magnitude. First stage Ti-6Al-4V fan blades were LPB processed using a conventional 4-axis CNC machine tool. LPB dramatically improved surface finish with negligible blade distortion and produced compressive residual stresses of -690 MPa (-100 ksi) through the entire thickness of the blade leading edge. Fatigue testing demonstrated that the deep compression of LPB provided a 3X improvement in HCF endurance limit, complete tolerance of FOD up to 1.3 mm (0.050 in.) deep, and an order of magnitude improvement in fatigue life. Damage tolerance for the TI-6AL-4V fan blade was improved by an order of magnitude.