Chapter introduction

Abstract

High-power, continuous-wave CO₂ lasers are finding increasing use in engineering applications for improving the surface properties of hardness, wear, corrosion and fatigue by transformation hardening, surface melting, surface alloying and surface cladding. The beneficial effects are achieved by modifying the microstructures and surface composition using this uniquely localized and flexible energy source. In the following ten papers it will be seen that the laser is capable of generating ultrafine to amorphous microstructures, sometimes involving metastable phases due to the rapid solidification possible. Furthermore, due to the steep thermal gradients resulting in considerable convection, homogeneous surface layers can be obtained. Clad layers can be formed by feeding an appropriate material into the laser melt pool. These layers can be made with a fusion bond and low dilution and offer advantages over present techniques. A characteristic of laser treatment is the production of residual stresses which can be compressive or tensile. Sufficient work has now been done to identify the associated problems in many cases. The laser currently offers to industry one of the most flexible energy sources, and all of the processes described in this chapter could be coupled for full automation.