Effect of laser surface hardening on En18 (AISI 5135) steel

Laser surface hardening is an effective technique used to improve the tribo logical properties and also to increase the service life of automobile comp onents such as camshafts, crankshafts, lorry brake drums and gears. High po wer CO, lasers and Nd-YAG lasers are employed for localized hardening of ma terials and hence are of potential application in the automobile industries . All steel surfaces can be hardened with high power laser sources, the deg ree of hardenability and fineness in microstructure obtained depending on t he laser processing variables and on the absorption coatings employed. In t his investigation, the microstructrual features occurring in CO, laser hard ened En18 steel are discussed with the use of optical microscopic and scann ing electron microscopic analysis. Moreover, the correlation between the su rface temperature and cooling rate on the resulting hardness is explained. Theoretical thermal profile studies are made and their effect on the coupli ng coefficient values, hardness and the microstructural changes observed ar e discussed. The effect of laser hardening on wear resistance is described. (C) 1999 Elsevier Science S.A. All rights reserved.