Duplex surface treatments on AL7075-T6 alloy against fretting fatigue behavior by application of titanium coating plus nitriding

The improvement of fretting fatigue resistance of AL-7075 is studied using surface treatments including nitriding and titanium coating by hollow cathode discharge (HCD) and magnetron sputtering techniques. The experimental results indicate that surface nitriding reduces the fretting fatigue resistance of the material. Titanium coating, using HCD technique, may increase the fatigue life up to 85% at low working stresses, while at higher stresses the increase is not considerable. Titanium coating, using magneto sputtering technique, may increase the fatigue life up to 77% at low working stresses, while at higher stresses it gives rise to the reduction in fretting fatigue life. Duplex treatment including nitriding with no temperature control, plus titanium coating by HCD technique, gives rise to the reduction in fatigue life. Duplex treatment including nitriding with substrate's temperature control plus titanium coating by DC magnetron sputtering technique increases the fatigue life up to 185% at low stresses and up to almost 60% at higher stresses.