Heat treatment of cold spray coatings to form intermetallic layers

A new approach for the use of cold spray coatings is presented. Al cold spray coatings on Mg-Al-Zn were given a postspray heat treatment to form thick, continuous intermetallic layers of the MgAl and AlMg phases at the coating/substrate interface. This heat treatment is similar to a typical solutionising treatment and would be readily applicable in practice. The heat treatment produces intermetallic layers with significantly higher hardness and corrosion resistance than the AZ91 substrate material. In general the surface properties are close to those of bulk Al, and such a coating would provide a useful level of protection to Mg-Al-Zn alloys in service