Laser surface alloying applied on Ti-3Mo and Ti-10Nb sintered parts

Abstract

Laser surface treatments can be applied to sintered parts aiming to close porosity and produce properties gradients. In this work, the Ti-10Nb and Ti-3Mo alloys were produced by powder metallurgy and modified by laser surface alloying with preplaced Nb and Mo powders. The laser power was varied from 150 to 450 W, while other laser parameters were kept constant. Substrates and surface-modified layers were characterized by scanning electron microscopy, X-ray diffraction, and nanoindentation. Both sintered alloys presented α+β microstructure, and the pore-free surface layers were composed of α″ and α′ immerse in a β phase matrix. Higher laser powers produced deeper fusion zones, and, consequently, a higher dilution of the alloying element. The higher the laser power, the deeper the fusion zone, and the higher the alloying dilution. Mo preplaced powder allowed the attainment of thicker and more diluted surface layers under the same heat input. The surface-modified layers presented higher hardness than the substrate. The Ti-Mo surface layers' elastic modulus was slightly higher than that of the sintered Ti-3Mo substrate, and the Ti-Nb surface layers' elastic modulus was lower than that of the sintered Ti-10Nb substrate. The Ti-Nb surface layer processed at 300 W presented the most extensive presence of the β phase and the lowest elastic modulus.