Surface Modification Using High Power Lasers: Influence of Surface Characteristics on Properties of the Laser Processed Materials

摘要

A laser beam is a remarkable thermal source where a very high energy is concentrated, which, moreover, can be often transmitted easily though fibre optics and mirrors. Advantages of laser treatments are, first, those of any local treatment, e.g. a limited deformation of the treated parts. In addition, one may claim a high flexibility compared to electron beam treatments for example. Treatments in air or in an inert or reactive gas can be applied with a high accessibility to zones to be treated. In the field of materials, the first application to be envisaged for laser, except for cutting and welding, was that of heat treatment, which means for laser users laser surface hardening based on quenching after heating at the solid state. Since this first application, numerous further treatments have been developed. These treatments involve superficial melting of the part to be treated, with or without further material feeding or, more recently, the laser shock phenomenon. This paper based on results of research studies carried out at Ecole des Mines de Paris reviews the main laser surface treatments which are already industrial or to be industrial within a rather short term. For every process, the principle and some fundamentals, characteristics of the treated surface and their influence on mechanical properties are given. Specific applications are then respectively given, featuring those to aircraft-aerospace industry. The influence of superficial damage, when occurred, is also discussed in the light of corresponding healing processes.