Multimodal powders : A new class of feedstock material for thermal spraying of hard coatings

We are developing a new class of High Velocity Oxy-Fuel (HVOF) thermal spray feedstock powders, which consist of aggregates of hard ceramic particles that are either mixed or coated with a more readily fusible nanophase binder. Thus, during thermal spraying, the nanostructured material undergoes rapid melting while the aggregated material is heated but not necessarily melted. A dense coating is formed when the molten nanomaterial fills the available pore spaces between the heated and softened aggregates, providing a strong and tough matrix for the spray-deposited material. Such multimodal coatings combine moderate hardness with exceptional abrasive wear resistance. Characteristics of the multimodal feed powders, along with the structure and properties of the resulting coatings, are described in this paper. (Author)