Surface Modification of Aluminum by Laser Alloying with TiO2 Powder

The aluminum surface was modified by CO2 laser beam irradiation onto a surface coated 0.2mm thick with TiO2 powder. Surface and cross sectional views of melted layers formed under different laser irradiating conditions were observed by optical microscope. Cross-sectional hardness was evaluated by micro-Vickers hardness measurement, and the composition was studied by microdiffraction analysis. A hard alloyed layer formed on the surface of the Al substrate at laser power exceeding 2kW. At less than 2kW, a clad layer formed. The alloyed layer consists of eutectic Al+Al3Ti. Hardening in the alloyed layer is caused by crystallization of the Al3Ti intermetallic compound formed by a reaction between substrate Al and Ti separated from TiO2. TiO2 powder is thus useful in laser alloying.