Cold Spraying: A Novel Technique for Constructing Functional Coatings by Impacting Particles
Thomas Klassen, Director, Institute of Materials Technology, Helmut Schmidt University Hamburg, Germany
February 16, 2007
Abstract
Thermal Spray coatings are in widespread use for turbine blades in airplanes or water power plants, or for providing improved wear or corrosion resistance in various applications. In thermal spraying, well-tuned amounts of thermal energy and kinetic energy are employed to form dense coatings by impacting droplets or powders of metals, composites, or alloys. A bottleneck of conventional thermal spray technology is the high temperature of operation, which may lead to phase transformations in the spray material, or to increased oxidation if sprayed in ambient atmosphere. The recently introduced technique of cold spraying mainly relies on the high kinetic energy of solid particles impinging the substrate surface. Since the spray material is only exposed to an inert process gas and to well tuneable temperatures below the melting point of typical feedstock powders, this method is most suitable for heat and oxidation sensitive materials. Moreover, heat-sensitive substrates, e.g. light metal alloys or selected polymers, can be coated. Comparisons with related processes, such as explosive powder compaction and macroscopic impact experiments, as well as computer simulations visualize the bonding process and allow for extracting critical parameters. Various examples of cold-sprayed coatings for current and potentially new applications will be presented, including more efficient heat exchangers, high power electronics, and catalysis.
Biography
Thomas Klassen studied Physics in Dortmund, Germany, and received his Ph.D. in Engineering from the Technical University of Hamburg-Harburg, Germany. He spent two years as a post-doc at the Materials Science Lab, University of Illinois at Urbana-Champaign, before becoming a group leader at GKSS, a National Research Center in Germany. In 2005, he finished his habilitation thesis on Nanostructured Materials, and joined the faculty at the Helmut Schmidt University in Hamburg.