P A Carvalho, N Braz, M M Pontinha, M G S Ferreira, W M Steen, R Vilar, K G Watkins

An automated workstation for variable composition laser cladding was developed and its potential for rapid alloy scanning was demonstrated. Ternary alloys of the Co-Ni-Al system were prepared using variable powder feed rates; the aim was to produce linear composition variations along the length of the laser-clad tracks. The chemical compositions and the hardnesses of the alloys corresponding to different zones of the tracks were evaluated. Microstructural characterization was performed by scanning electron microscopy and X-ray diffraction. To assess the corrosion behaviour of the alloys, electrochemical polarization tests were carried out in aerated 3% NaCl. The deviations from linearity of the composition variations were explained, the microstructure evolution was studied, a relationship between the hardness and the microstructure was found, and some trends in the corrosion behaviour were defined.