AeroMat Home      ASM Homepage
Back to "Emerging Materials and Processes II - Processes" Search
  Back to "Emerging Materials and Processes" Search  Back to Main Search

Tuesday, June 24, 2008 - 8:30 AM

A Novel Method to Spray WC-Co Using Portable Low Pressure Cold Spray Technology

J. Villafuerte, Centerline Windsor Ltd, Windsor, ON, Canada

Title:  "A Novel Method to Spray WC-Co Using Portable Low Pressure Cold Spray Technology”

 Author: Julio Villafuerte, Ph.D., P.Eng.,
Corporate product development manager for CenterLine
(Windsor) Ltd., Windsor, Ontario, Canada, Julio.villafuerte@cntrline.com

 Cold spray is a new solid-state spraying process capable of producing thick metallic coatings or freestanding deposits on a diversity of surfaces. The process takes place at low temperatures, thus avoiding thermal effects such as oxidation, tensile residual stresses, and metallurgical transformations associated with conventional thermal spray processes.  However, due to the nature of the solid-state bonding, the use of traditional cold spray methods has been limited to metals and other materials displaying a certain level of ductility.  A large number of coating applications call for a combination of corrosion, wear, and thermal resistance, requiring materials that cannot typically be sprayed using cold spray.  High Velocity Oxyfuel (HVOF) spraying of WC-Co is one of a number of methods to provide thermal barrier, wear, and corrosion proof coatings.  The use of HVOF in spraying WC-Co has been particularly widespread to replace hard chrome plating in light of recent OSHA regulations limiting the use of processes that release Hexavalent chromium (Cr+6), a well-known carcinogen.  In this paper, we present a different method to cold spray WC-Co cermets using a portable low-pressure system.  The coatings show attractive physical and mechanical properties, without the aggravations associated with elevated process temperatures such as decarburization, oxidation, metallurgical transformations, and residual stresses.  This method can also be applied to cold spray other materials such as Ti-based alloys, Ni-based alloys, steels, Tungsten, Tantalum, ceramics (TiC, VC, WC, HfC, ZrC, NbC, Cr3C2, TaC, Al2O3, Cr2O3, TiO2, ZrO2, TiN, AlN, BN, Si3N4), intermetallics (Ni3Al, Ti3Al), and other cermets.


Summary: Cold spray is a new solid-state spraying process capable of producing thick metallic coatings or freestanding deposits on a diversity of surfaces. The process takes place at low temperatures, thus avoiding thermal effects such as oxidation, tensile residual stresses, and metallurgical transformations associated with conventional thermal spray processes. However, due to the nature of the solid-state bonding, the use of traditional cold spray methods has been limited to metals and other materials displaying a certain level of ductility. A large number of coating applications call for a combination of corrosion, wear, and thermal resistance, requiring materials that cannot typically be sprayed using cold spray. High Velocity Oxyfuel (HVOF) spraying of WC-Co is one of a number of methods to provide thermal barrier, wear, and corrosion proof coatings. The use of HVOF in spraying WC-Co has been particularly widespread to replace hard chrome plating in light of recent OSHA regulations limiting the use of processes that release Hexavalent chromium (Cr+6), a well-known carcinogen. In this paper, we present a different method to cold spray WC-Co cermets using a portable low-pressure system. The coatings show attractive physical and mechanical properties, without the aggravations associated with elevated process temperatures such as decarburization, oxidation, metallurgical transformations, and residual stresses. This method can also be applied to cold spray other materials such as Ti-based alloys, Ni-based alloys, steels, Tungsten, Tantalum, ceramics (TiC, VC, WC, HfC, ZrC, NbC, Cr3C2, TaC, Al2O3, Cr2O3, TiO2, ZrO2, TiN, AlN, BN, Si3N4), intermetallics (Ni3Al, Ti3Al), and other cermets.