Deposition of Ti-6Al-4V using a high power diode laser and wire, Part II: Investigation on the mechanical properties

The deposition with high power diode laser and Ti6Al4V wire was verified as a process which can provide a high deposition rate with good quality. Sound mechanical properties of the deposited parts are the prerequisites for the real applications of this process. In this pamper, the main mechanical properties including micro-hardness and tensile properties were investigated. Single bead walls were deposited. Test pieces were machined from the deposited walls according to the British standard for the mechanical tests. The epitaxial columnar grains were found growing parallel to the building direction. A band region was observed between two deposited layers, which resulted from the remelting of previously deposited layer and multiple thermal cycles that had occurred with each subsequent deposition pass. The results showed that with the same laser power, the built samples with higher traverse speed possess similar or slightly higher hardness than the samples built with lower traverse speed. The hardness varied less than 10% with different sets of parameters. The investigations on the tensile properties were carried out with the samples as deposited and stress relieved at 700 degrees C in an air circulating furnace for 2 h. The as deposited samples showed better tensile properties than the stress relieved ones. This results from the reduction of the compressive residual stresses and the coarser microstructure after stress relief. The tensile properties also showed dependence on the direction of the test carried out. All the examined tensile properties of the as deposited samples matched properties of the as cast and wrought material. (C) 2008 Elsevier B.V. All rights reserved.