Cold gas-sprayed titanium aluminide coatings: production and characterization

Abstract

Commercial titanium alloys, which are used in automotive and aerospace applications, are characterized by a low specific weight, high strength and an excellent corrosion resistance at relatively low temperatures. In some applications, they are exposed to a combination of high temperatures and mechanical loading as well as wear damage. However, the oxidation and abrasive resistance of titanium at high temperatures are rather poor; alloys such as Ti6Al4V have applications which are limited to temperatures below 500ºC; therefore it is of interest to increase their application temperatures. Several methods have been employed to increase the oxidation resistance to 900ºC. Among them, the use of titanium aluminide coatings has been considered of interest, especially the titanium trialuminide, which possesses enough aluminium content to form protective alumina layers. Some approaches to this strategy have included the use of conventional thermal spray technologies. In the present work, we proposed the use of the Cold Gas Spray (CGS) process to first try to form γ-TiAl coatings on Ti6Al4V substrates. Due to some handicaps given by the low deformability of such powder alloy, γ-TiAl+Al composite coatings were produced and annealed afterwards to form the TiAl3. These coatings have been characterized from the microstructural point of view as well as their wear resistance and oxidation performance