Influence of laser cladding on the surface hardness of small-diameter metallic wire substrates

In this study, a laser beam is used to clad stellite or cermet on various m etallic wires. One aim is to realize a coating with a high volume compared with that of the substrate (ratio about 1/5) without the use of auxiliary c ooling. The thermal treatment induced during the coating can modify the pro perties of the wire, for instance the restoration of the structure of the i nitially cold drawn wire. This change of structure depends on the temperatu re reached in the wire and on the cooling rate. In order to control the hea t-affected zone (HAZ) in the wire, the thermal gradient in the cross-sectio n is calculated under the laser beam, and results are correlated with micro hardness profiles. It is shown that the HAZ is limited by the temperature o f restoration, beginning at about 1300 K. (C) 2000 Published by Elsevier Sc ience S.A. All rights reserved.