Laser-assisted direct manufacturing of functionally graded 3D objects

Composition gradients of different types were produced in three-dimensional (3D) objects by means of a repetitive deposition process to manufacture functionally graded materials (FGMs). Each layer of about 30-mum thickness is created by coaxial powder injection into the working zone along with the laser beam through a specially designed nozzle. The influence of two different laser sources, pulse-periodic Nd:YAG (wavelength 1.06 mum) and quasi-continuous wave CO2 (wavelength 10.6 mum), on the process has been studied. Since the former source provides better beam quality, the pulse-periodic Nd:YAG laser seems preferable for developing FGM components. The technique used allows developing predefined composition gradients by an appropriate change of the powder composition during the layer deposition process. The layered FGM samples were examined by metallography, microhardness measurements and SEM analysis. The compositional gradient can be smooth or sharp. This process also allows development of periodic multilayered structures. The SEM analysis showed that the minimal transition zone between two different alloys is only about 70 mum for a given condition. Thus, development of FGM structures by the above process seems feasible. (C) 2004 Elsevier B.V. All rights reserved.