2. Pure Metal, Metal Composite & Mixed Powders

Pure-metal, intermetallic-compound, and metal-mixture powders are important thermal spray feedstocks for corrosion protection, repair, wear resistance, high-temperature service, electrical conductivity, and multifunctional surface engineering. Selection should be based on service environment, required coating properties, process compatibility, and total lifecycle cost.

Pure-metal powders include aluminum, zinc, copper, nickel, and molybdenum. Their key advantages are simple composition, ductility, conductivity, corrosion protection, and cost-effective processing. Zinc and aluminum are widely used as sacrificial coatings for steel bridges, offshore structures, storage tanks, pipelines, and marine equipment. Wire arc spray and flame spray are commonly preferred for large-area corrosion protection because of their high productivity and relatively low cost. Copper powders are used for electrical contacts, bus bars, heat-management components, and dimensional restoration; plasma spray and cold spray are suitable when conductivity and low oxidation are important. Nickel powders are used for bond coats, shaft repair, and corrosion-resistant overlays, while molybdenum is applied to piston rings, synchronizer rings, and other friction or wear surfaces.

Intermetallic powders, such as NiAl, Ni₃Al, FeAl, Fe₃Al, TiAl, MoSi₂, and Mo-Si-B, provide superior oxidation resistance, hot-corrosion resistance, and strength retention at elevated temperatures. Their main limitation is relatively low room-temperature ductility. NiAl is widely used as a metallic bond coat beneath ceramic thermal barrier coatings on gas-turbine components. FeAl and Fe₃Al can protect boiler tubes, petrochemical equipment, and power-generation components. MoSi₂ and Mo-Si-B are candidates for extreme-temperature oxidation protection. APS, HVOF, and vacuum plasma spray are commonly selected depending on the required coating density and oxidation control.

Metal mixtures and composite blends enable tailored properties. Examples include Ni–Al and Fe–Al blends for post-spray intermetallic formation, Cu–Al for conductive lightweight layers, Al–Si for automotive repair, Ni–graphite for self-lubricating surfaces, and metal–ceramic blends for wear-resistant shafts, valves, and pumps. Cold spray is particularly useful for blended powders because it limits in-flight oxidation and can preserve constituent phases before heat treatment.

Future applications include hydrogen-energy systems, battery and power-electronics thermal management, smart conductive coatings, additive repair, advanced boiler protection, concentrated solar power, hypersonic aerospace systems, and high-temperature turbine coatings. In all cases, the best powder is the material-process combination that delivers the required performance with the lowest total lifecycle cost.