Cold Spray Coating Technology for Metallic Components Repairing

Abstract

Cold spraying is a coating technology on the basis of aerodynamics and high-speed impact dynamics. In this process, spray particles (usually 1–50 mm in diameter) are accelerated to a high velocity (typically 300–1,200 m/s) by a high-speed gas flow that is generated through a convergent-divergent de Laval type nozzle. A coating is formed through the intensive plastic deformation of particles impacting on a substrate at a temperature below the melting point of the spray material. It can be considered a safe and green technology because of the absence of a high-temperature gas jet, radiation, and explosive gases. The coatings formed using the cold flow deposition processes are dense and oxide-free. The cold flow deposition process has emerged as an important alternative to other thermal spraying processes. An example of a key application of the cold spray process is the recovery of costly aircraft parts during overhaul and repair. Cold spray also can be used in the development of unique materials and for the production of actual parts. Cold spray can be used to produce a new class of materials that could not be achieved by conventional ingot metallurgy. The cold spray process represents leading edge technology and provides superior performance over conventional technologies. Even if it has great application potentials in aerospace, automobile manufacture, chemical industry, etc., there are still many fundamental aspects to be uncovered. Because adhesion of the metal powder to the substrate and deposited material is achieved in the solid state, the characteristics of cold spray deposits are quite unique. Cold spray is suitable for depositing a wide range of traditional and advanced materials on many types of substrate materials, especially in non-traditional applications that are sensitive to the temperature of the process. Cold spray is capable of potentially providing restoration, sealing, surface modification, wear resistance, thermal barriers, heat dissipation, rapid prototyping, aesthetic coatings, fatigue resistance and many other applications without the undesirable effects of process temperatures or metallurgical incompatibilities among materials. It can also be used to increase the heat resistance of a material. Research into improving the cold spraying technology is still being conducted worldwide today.