Influence of detonation gun sprayed alumina coating on AA 6063 samples under cyclic loading with and without fretting

The influence of detonation gun sprayed alumina coating on Al-Mg-Si alloy (AA 6063) test samples subjected to cyclic loading with and without fretting was studied in the present work. Coated samples were grounded to have coatings of two different thickness values, 40 and 100 μm. Both 40- and 100-μm-thick coated specimens experienced almost the same but slightly higher friction force compared with uncoated samples. Under plain fatigue loading, 100 μm coated specimens exhibited inferior lives due to the presence of lower surface compressive residual stress compared with uncoated and 40-μm-thick coated samples. Under fretting fatigue loading, uncoated specimens exhibited inferior lives compared with coated samples owing to the very low hardness of the uncoated specimens (80 against 1020 HV0.2). The reason for the superior fretting fatigue lives of 40-μm-thick coated samples compared with 100-μm-thick coated samples was the presence of relatively higher surface compressive residual stress in 40-μm-thick coated specimens.