Fabrication of Ti-Al intermetallic compound coatings by cold spraying

In the present study, a Ti-Al coating was fabricated by cold spraying of powder mixture of Ti-50Al (at.%) assisted with annealing treatment. The deposition behavior of Ti-Al powder mixture and microstructural characteristics of as-sprayed and annealed Ti-Al coatings are characterized. The effect of annealing temperature on the phase structure and microstructure evolution is also investigated. It was found that the composite coating exhibits a dense microstructure and aluminum constitutes the matrix in which the deformed titanium particles are uniformly distributed. After heat treatment at 550^oC, TiAl3 and TiAl was appeared in the Ti-Al coatings. With the increase of temperature during annealing, the content of Ti-Al intermetallic phases is increased. The titanium particles in Al matrix were fully consumed via compounding reaction with Al at 600^oC. While the porosity in the as-sprayed precursor deposits was about zero, significant porosity developed during heat treatment and the sources for this are discussed.