MICROSTRUCTURE AND PROPERTIES OF LASER-PRODUCED TI-AL FUNCTIONALLY GRADIENT CLAD

The microstructure and oxidation and erosion resistance of three laser clad layers, namely, Ti-14.5 Al-3.7V, Ti-17 Al-3.7V, and Ti-30 Al-2.8 V (all wt-%), have been investigated. Using a continuous wave CO2 lase r and powder feed technique, three fully overlapping clad layers were deposited vertically to produce a Ti-Al functionally gradient coating on a commercial purity Ti substrate. The laser processing parameters w ere: 1.8 kW laser power, 3 mm laser beam diameter, 5.3 mm s-1 traverse speed, and 4.2 g min-1 powder feedrate. The results of the microstruc tural examination showed disordered martensite alpha' in the first lay er, ordered martensite alpha'2 in the second layer, and dendrites of a lpha2 with interdendritic regions of alpha2 + gamma in the third layer . Oxidation tests showed a significant improvement of oxidation resist ance with increasing Al content. The erosion resistance of the third l ayer was inferior to that of the substrate, whereas the second layer e xhibited superior resistance compared with the substrate.