Influence of the overlapped area on the corrosion behaviour of laser treated aluminium alloys

Laser surface treatments offer significant potential for improvement of materials properties such as corrosion performance and wear resistance. In large area applications, overlapping of individual tracks corresponding to the width of the laser beam is often required. This involves the heat treatment of a region adjacent to the previous track with microstructural changes such as precipitate coarsening and microsegregation at the overlap regions, which can lead to detrimental effects on the corrosion performance. This paper reports the characteristics and corrosion behaviour of the overlapped areas in the laser melting and alloying with Cr, W, Zr-Ni or Ti-Ni of 2014 aluminium alloy. It is shown that microsegregation occurs within the planar front zone of laser melted samples and microstructural coarsening occurs in the heat affected zones caused by the reheating effect at the laser track overlaps. Electrochemical testing has indicated that microsegregation within the overlapped areas leads to initiation of pitting corrosion in most of these cases. (C) 1998 Elsevier Science S.A. All rights reserved.