Surface Characterizations of Fretting Fatigue Damage in Aluminum Alloy 7075-T6 Clamped Joints: The Beneficial Role of Ni–P Coatings

Abstract

This paper aims to characterize the surface damage as a consequence of fretting fatigue in aluminum alloy 7075-T6 plates in double-lap bolted joints through XRD, surface profilometry, and SEM analyses. The main focus was on the surface roughness and chemical phase composition of the damaged zone along with the identification of fretting fatigue crack initiations over the surface of the material. The surface roughness of the fretted zone was found to increase when the joint was clamped with a higher tightening torque and tested under the same cyclic loading. Additionally, MgZn2 (η/ή) precipitates and ZnO phase were found to form onto the surface of uncoated aluminum plate in the fretted and worn zones. The formation of the ZnO phase was understood to be a result of frictional heat induced between the surface of contacting uncoated Al 7075-T6 plates during cyclic loading and exposure to the air. The beneficial role of electroless nickel-phosphorous (Ni–P) coatings in minimizing the fretting damage and thus improving the fretting fatigue life of the aluminum plates was also studied. The results showed that the surface roughness decreased by approximately 40% after applying Ni–P coatings to the Al 7075-T6 plates.

Experimental and Numerical Investigations of Fretting Fatigue Behavior for Steel Q235 Single-Lap Bolted Joints

“…Furthermore, the effects of clamping pressure and friction force on the fretting fatigue performance of Al 7075-T6 bolted plates with electroless Ni-P coatings were examined based on a 2D finite element model, in which Ni-P coatings with thickness of 40 m were separately modeled with fine meshes, and the mechanical properties were determined using nanoindentation method [16]. Recently, Oskouei et al also investigated the surface roughness and chemical phase composition of the fretting damaged zone for Al 7075-T6 bolted plates; the influence of fretting fatigue damage on the surface roughness for Ni-P coated and uncoated Al 7075-T6 bolted plates was examined [17].…”

Effects of Aging Temperature, Time, and Pre-Strain on Mechanical Properties of AA7075

“…3 (b). Based on the peaks on the graphic, it is proven that the microstructure consists of Al and MgZn 2 phases as reported in references of 40,41 . For 30 minutes aging time, no MgZn 2 phase was observed at all aging temperatures (120, 160, and 200 o C) as displayed in Fig.…”

Investigation of the properties of Al7075-HTC composites produced by powder metallurgy

“…16,30,31 Al 7075 and its composites possess strong peaks at 2h ¼ 38.33 , 44.58 , and 64.91 which are related to a-Al. 32 On the other hand, characteristic peak of Al 4 C 3 or other metallic carbides which can cause to decrease of strength of composites was not detected so this indicated better potential for mechanical properties. [33][34][35] The densities and porosities of samples are presented in Table 2.…”