COATING BY LASER-SURFACE TREATMENT

The application of optical engineering in industrial processing is gaining greater acceptance. The range of surface treatment processes available goes all the way from transformation hardening, annealing, shock hardening and bending (as processes which do not involve melting) to processes which involve melting such as surface melting, surface alloying, surface cladding and those processes which involve some form of photochemistry such as laser chemical vapour deposition, laser physical vapour deposition and stereolithography. One of these processes, laser cladding, has been recently extended at University of Liverpool to provide a technique of rapid alloy scanning whereby variable composition laser clad tracks can be laid down by the laser thus giving the whole range of compositions in the alloy system in a single sample. Evaluation of specimens of this type can be carried out by a range of micro testing techniques including corrosion testing procedures. Laser surface treatment processes available for the production of corrosion resistant surfaces are reviewed. These include surface melting, surface alloying and surface cladding procedures. Consideration is then given to the new variable composition laser melt track technique with particular reference to the rapid prototyping of corrosion resistant alloys.