Excimer laser induced surface nitriding of aluminium alloy

This study describes a technique for the growth of thin nitride layer on aluminium alloy samples by direct laser synthesis with the advantages of good adhesion and localisation. The laser irradiation process is performed using an XeCl excimer laser (lambda = 308 nm, 50 Hz) under a nitrogen atmosphere. The laser induced plasma interacts with the melted sample surface resulting in nitrogen atom diffusion and reaction into the depth of the sample. Plasma spots were overlapped by two dimensional laser beam displacement to ensure the complete coating of the surface with a specified laser fluence (1.6 J/cm(2)) and number of pulses (500), while not removing of the nitride layer already synthesised. Under these conditions, the diffusion layer penetrates a few mu m deep, but its crystalline quality is preserved. Interesting information on the layer formation and composition are drawn from nuclear analysis (RBS and NRA) to determine the nitrogen and oxygen (contaminant) concentration profiles. (C) 1998 Elsevier Science B.V.