Because early attempts to exploit the cold gas-dynamic spray process were not commercially successful, the only evidence of pioneering work in this field seems to be the record preserved in US patent documents. The first such US patent was granted over one century ago to Samuel H Thurston. His US patent application titled: Method of Impacting One Metal Upon Another, was filed on March 23, 1900. The description of the method issued on August 12, 1902 as US patent 706,701 included: “metal particles driven by pneumatic pressure against the surface to be coated with such force as to embed the metal of the said particles in the surface of the metal against which they are driven and incorporate the two together, thus forming a stable and efficient metal coating of one metal upon another which is irremovable without removing the metal of the plate of object thus coated.”

This patent would be followed more than a decade later as a Thermal Spray process variation by Max U Schoop in a pivotal US Thermal Spray patent. While the International Thermal Spray Association (ITSA) recognizes his US 1,133,507, Apparatus for Spraying Molten Metal and Other Fusible Substances patent (Filed February 19, 1914 issued March 30, 1915) as one of the founding records for the thermal spray process; it is one of his earlier patents that links him to the history of cold gas-dynamic spray. US patent 1,128,059, Method of Plating or Coating with Metallic Coatings filed August 7, 1911 and issued on February 9, 1915 includes the claim: “The process of producing coherent metallic coatings, which consists in projecting finely-divided, unmolten metal and metal oxid onto a surface to be coated with sufficient force to form a non-porous, homogeneous coating on said surface.”

Another four decades would pass before the US patent office would consider another cold gas-dynamic spray process patent application. US patent 3,100,724, Device for Treating the Surface of a Workpiece was filed on September 22, 1958 by Charles F Rocheville, and issued on August 13, 1963. His invention incorporates a sequential pair of converging-diverging nozzles and the “object of this invention is to direct a finely divided powdered material against a surface at supersonic velocities to cause said material to adhere in the pores of the part, and in some instances to fuse thereon.”

More than twenty years later the process would be discovered once again at the Institute of Theoretical and Applied Mechanics of the Siberian Division of the Russian Academy of Science in Novosibirsk. An accidental discovery during wind tunnel testing prompted a detailed investigation into the concepts behind high speed impact of particles to coat surfaces.

US patent 5,302,414, Gas-dynamic spraying method for applying a coating was filed on February 2, 1992 (with a PCT Filing date of May 19, 1990) by: Anatoly P Alkhimov, Anatoly N Papyrin, Vladimir F Kosarev, Nikolai I Nesterovich, and Mikhail M Shushpanov. This patent is considered by many to be the foundation for the modern high-pressure cold spray process. The patent abstract states: “A cold gas-dynamic spraying method for applying a coating to an article introduces into a gas particles of a powder of a metal, alloy, polymer or mechanical mixture of a metal and an alloy, the particles having a particle size of from about 1 to about 50 microns. The gas and particles are formed into a supersonic jet having a temperature considerably below a fusing temperature of the powder material and a velocity of from about 300 to about 1,200 m/sec. The jet is directed against an article of a metal, alloy or dielectric, thereby coating the article with the particles.” Work in the U.S. began in 1994, when Dr. Papyrin arrived from Russia and the National Center for Manufacturing Sciences sponsored a technology demonstration program.

Somewhat in parallel to this commercialization attempt, another group in Russia continued to refine the cold gas-dynamic spray process and eventually led to the founding of the Obninsk Center for Powder Spraying (OCPS) in 1992. They successfully refined the design of a system that did not rely on driving powder-laden inert gas through the throat of the venturi with high pressure. The innovation behind their Dymet^® low-pressure cold gas-dynamic spray process was acknowledged with the granting of US patent 6,402,050, Apparatus for gas-dynamic coating. This US patent was filed on May 18, 1999 by Alexandr I Kashirin, Oleg F Klyuev, and Timur V Buzdygar (PCT filing date October 27, 1997) and the patent was issued June 11, 2002. The abstract states that “The apparatus is comprised of a compressed air source which is connected by a gas conduit to a heating unit whose outlet is connected to a supersonic nozzle inlet in which a supersonic portion is connected by a conduit to a powder feeder. Compressed air of pressure Po from the compressed air source by the gas conduit is delivered to the heating unit to be heated to the required temperature. The heated air enters the supersonic nozzle in which it is accelerated to a speed of several hundred meters per second. The powdered material is passed from the powder feeder by the powder feeding conduit to the supersonic nozzle portion in which it is accelerated by the air flow at section of the nozzle from the injection point to the nozzle outlet.”

CenterLine has worked since 2003 to commercially exploit this patent in North America. This includes significant ongoing investments in scientific research to understand the physics of the process, as well as practical development of robust equipment that can finally allow us to realize the potential contemplated my Mr. Thurston more than 100 years ago.