Laser Surface Melting and Alloying of Titanium

Abstract

In recent years there has been rapid development in the use of lasers for the surface treatment of metals (1–3). Titanium is particularly susceptible to oxidation during this process, but it can be treated successfully under normal laboratory conditions providing that a good shrouding system is used. The result is that a flat, relatively smooth surface profile can be obtained. The depth of melting can be controlled by varying the laser parameters. Surface alloying may also be successfully achieved by using either preplaced powders, such as carbon, or electroplated layers, such as nickel, or by introducing an alloying gas into the shrouding system, such as nitrogen (4). A combination of these processes may also be used, as in the case of carbonitriding. The resultant alloyed zone modifies the surface characteristics of the substrate. Nickel affects the electrochemical properties, nitrogen affects the hardness and, consequently, the wear properties of the metal. Nitriding is discussed in detail here and an indication of the structure of the melt zone is given.