JOURNAL DE PHYSIQUE N Colloque C7, supplkment au Journal de Physique 111, Vol. 1, dkembre 1991 HIGH TEMPERATURE PROPERTIES OF LASER ALLOYED TITANIUM A. FASASI, M. PONS and A. GALERIE Laboratoire Science des Surfaces et Matiriaux Carbonis) URA CNRS no 413, ENS dJElectrochirnie et d'Electromktaflurgie de Grenoble, Imtitut National Polytechnique de Grenoble, Bf? 75, Domaine Universitaire,F-38402 St-Martin dJHtres, France Abstract - Surface alloys are of great interest for improving the mechanical and/or chemical properties of the near surface region of metallic materials. Surface alloy formation by laser melting involves the base metal and one or several foreign elements, introduced either in a predeposited slurry or directly in the melt pool by the means of a power feeder. Surface alloys were produced on titanium by laser irradiation of predeposi- ted aluminium and silicon powders. It was observed that hardness increa- sed with silicon content and carbon dissolution. The maximum value achieved was as high as 1100 Hv without the presence of carbon. It was also observed that laser aluminization improved isothermal as well as cyclic oxidation resistance while the presence of carbon was detrimental. The addition of silicon led to a decrease of the minimum concentration of aluminium necessary to form a continous and protective layer of A1203. 1. INTRODUCTION The earlier works on ligh temperature oxidation kinetics of bulk Ti-A1 alloys (1, 2) have shown that 25 to 64 atom % aluminium is necessary to have a distinct formation of A1 0 on the surface of this alloy. The titanium aluminides like Ti A1 and TiAl have good 2 3 strengths but cannot withstand temperature greater than 923 and 1323 K respectively in an oxidizing environment. Addition of silicon to titanium (3, 4) improved its resistance to scaling due to the formation of a protective silica layer which prevents the inward diffusion of oxygen. The use of laser on direct write metalisation for microelectronic purposes using polymeric substances has been going on for some time (5) but it is only recently that Pons et al. (6) presented a new working possibility which consisted of chemical reduction of metal salts in polymers, followed by alloying in the liquid state. Here, we describe simultaneous aluminization and siliconization of a commercial titanium alloy (TA6V4) by laser melting for modification of its surface properties like microhardness and oxidation resistance. 2. EXPERIMENTAL PROCEDURES Alcoholic and polymeric mixtures of aluminium and silicon were used. The preparation of the alcoholic mixture and the characteristics of the laser employed has been described elsewhere (7). In the polymeric mixture, 2 g of aluminium, 1,4 g of silicon were mixed with 3 g of polyethylene glycol (PEG). The mixture was heated to the melting point of the polymer (343 K), brushed onto the 1200 Sic grit polished TA6V4 specimens of 1.5 x 1.3 x 0.3 c m dimension and left to dry in air. The thickness of the deposited layers were 200 pm. Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jp4:1991712