This Phase I Small Business Technology Transfer (STTR) project will test the feasibility of making bioactive coatings from hydrothermal nanostructured hydroxyapatite (n-HA) and micron-size titanium. The two components will be processed by attritor milling or mechanofusion to make a nanocomposite feed stock. Cold Gas Dynamic Spray (CGDS) processing will be used to form a porous titanium coating on titanium substrates that contain a high volume fraction of n-HA crystallites. It is expected that such coatings on bioimplants, for example, would promote the in-growth of natural bone, facilitating attachment of the implant to surrounding bone material. CGDS processing is a new way to form functional coatings from powder feedstocks. Powder particles are accelerated to supersonic speeds (Mach 2) achieving high kinetic energy sufficient to form a dense coating upon impact with a substrate. CGDS processing differs from conventional spray processes in that it does not rely on thermal energy to melt the feed powder or to promote bonding. Instant bonding is due solely to the dissipation of kinetic energy on a time scale of <1 microsecond. Since the processing temperature is typically <200 C, CGDS processing is ideal for maintaining the nanograin-size and temperature sensitive crystal chemistries such as in n-HA biomaterials. The CGDS process will prove to be a versatile, cost-effective way to fabricate functional surfaces that exploit the properties of nanostructured powders. Since CGDS can coat large areas, complex shapes, and can be applied to a variety of materials it will have wide commercial impact applications for human medical and veterinary prosthetic implants.