The influence of duplex surface treatment including a Cr/CrN nanolayered coating deposited by cathodic arc physical vapor deposition (CAPVD) and an alumina layer coated by hard-anodizing method on the fretting fatigue strength of Al7075-T6 alloy is studied in this investigation. Although fretting fatigue life of both single Cr/CrN coated alloy and Cr/CrN coating deposition onto hard-anodized alloy was increased in high cycle fatigue (HCF) regime, employing an alumina layer as a pretreatment for the Cr/CrN deposition enhanced the life improvement in the HCF regime. In low cycle fatigue (LCF) regime, despite a decrease in fretting fatigue life of both Al7075-T6-coated alloys, using the alumina layer beneath the Cr/CrN coating resulted in mitigation of fretting fatigue life deterioration. Interestingly, a single-hard-anodized specimen represented a completely different variation trend of fretting fatigue life in HCF and LCF regimes. Unlike the as-received and single-hard-anodized specimens, Cr/CrN-coated specimens did not bear the maximum axial stress, 260 MPa. Partial slip regime was mostly seen at the contacting area
