Effects of peening duration on surface and wear properties of aircraft graded AA2017 alloy

Abstract

This investigation addresses the effects of peening duration during SP on surface properties of AA2017 alloy. SP performed with different durations (0, 70, 140 and 210 s) and imparts the modification in the surface region. Alloy strength and structural parameters like crystallite size (D), dislocation density (ρ) microstrain (ε) and lattice constant (a) are increased with SP duration till 140 s. After 210 s, these properties declined due to the effect of softening caused by rise in surface temperature through over peening duration, and exhibited dynamic recovery. Severe plastic deformation developed by SP, created rough surface in all SPed samples and shows responsible for low wettability, high contact angles and low surface energy in comparison with AR sample. The SP140 exhibited maximum hardness (234 ± 7.1 HV) and maximum residual compressive stress (RCS) (−51 MPa) as compared with that of AR sample shown 70 ± 2.1 HV and 20 MPa respectively. Also, the cross-sectional measurements over a thickness of 200 μm confirmed their improvement. These results favoured for SP140 sample to yield lower wear rate about 0.776 mm3/ KN-m compared to AR sample (1.046 mm3/ KN-m). Further increase in shot peening duration to 210 s induces softened layer by rise in surface temperature and presence of Cu as major alloying element in AA2017 exhibits superior thermal conductivity and resulted in detrimental effect on wear resistance. The combination of several factors such as structural parameters, RCS and hardness in the surface region of SP140 sample are responsible to develop the wear resistance of AA2017 alloy.