Experimental study of a six new ball-burnishing strategies effects on the Al-alloy flat surfaces integrity enhancement

Abstract

In the literature, the most studies conducted on the flat surface ball-burnishing process have been focused on the most important classical factors like burnishing speed, lateral feed, and the ball-burnishing load or pressure on the treated surfaces integrity enhancement. In this research, ball-burnishing strategies are studied as a new ball-burnishing factor. The aim of this research is to show the improvement of the flat surface integrity of 2017A-T451 aluminum alloy using six new ball-burnishing strategies. Ball-burnishing tests were conducted in two passes using the recommended values of the ball-burnishing factors (the penetration depth a b is 40 μm, the linear ball-burnishing speed V b is 500 mm/min and a lateral feed f of 0.2 mm). Two ball-burnishing strategies in two successive and perpendicular passes to the machining direction and four ball-burnishing strategies in two crossed passes have been designed and tested to improve the flat surfaces integrity of the samples. The characterization and the micrographic observations of the ball-burnished surfaces show that using the best ball-burnishing strategy leads to a great enhancement in surface quality. The latter is predicted by a gain in average roughness Ra of 81 %, an improvement in the mean spacing of profile irregularities Sm of 34 %, an enhancement in surface Nano-hardness HIT of 17 %, and sub-layer hardness betterment up to a depth of 500 μm.