Functionally gradient materials for thermal shock have been developed by a laser spraying method. They consist of titanium and titanium nitride. A pure titanium wire was melted by a high-energy-density carbon dioxide laser beam and a gas stream produced a fine spray of melted titanium particles which coated a mild steel substrate. The chemical compositions of the sprayed layer depended on the gas used. Different gases (argon, nitrogen and argon/nitrogen mixtures) produced coatings which comprised titanium, titanium nitride and mixtures of these components. The ratio of titanium nitride content to titanium in the sprayed layer was directly related to the argon/nitrogen ratio in the gas. Since the thermal expansion coefficients and the melting points of each layer are gradient through the coating, the laser-sprayed coating is expected to be applicable as a thermal shock absorbent or a thermal barrier coating.
