Supersonic Laser Deposition of Self-Lubricating Coatings

Supersonic Laser Deposition (SLD) is a coating and fabrication process combining cold spray (CS) with laser heating of the deposition zone. Laser heating increases deformation on impact, improving bonding for a given particle velocity, eliminating the need to use helium while retaining the advantages of CS; solid-state deposition, low oxidation and high build rate (≤ 10 kg/hr). Although solid lubricants offer advantages over liquid lubrication, remaining effective over a wide range of operating temperatures and loads, while simplifying sealing, their use is limited by current application methods. SLD enables the deposition of metallic coatings which incorporate solid lubricants into metallic coatings, onto a range of substrates. This paper details the powders and conditions used to deposit nickel/graphite using SLD, and the structure and tribological properties of the coatings produced. Co-efficients of friction below 0.14 were demonstrated for nickel/graphite coatings on aluminium substrates.

ВПЛИВ МОРФОЛОГІЇ ПРИРОДНІХ ГРАФІТІВ НА ЕКРАНУЮЧІ ВЛАСТИВОСТІ КОМПОЗИТНИХ МАТЕРІАЛІВ

Optimization of composition for a composite material based on graphite was done in order to increase the effectiveness of electromagnetic shielding. Morphological studies were carried out by optical and electron microscopy. Surface conductivity was determined by a four-probe measurement method. The effectiveness of electromagnetic shielding was studied by the level of attenuation of electromagnetic energy through the sample and the power level of the reflected electromagnetic wave in front of the sample. The dependence of surface conductivity and the efficiency of electromagnetic shielding on the particle size distribution of graphite in a composite material, as well as its density and thickness, has been established. It was experimentally approved that low-density carbon-graphite coatings containing magnetite were sufficiently effective for electromagnetic shielding. The density of the coating depends on their mechanical processing, as well as on the polydispersity of the graphite material. Shielding efficiency can be enhanced by combining layers of different density. A new concept for the manufacture of protective coatings for electromagnetic shielding was proposed taking in the account characteristics of graphite material such as polydispersity and particle structure. Particular attention was paid to the production of new carbon-graphite composites for the manufacture of screens and absorbers of electromagnetic radiation. The radio-absorbing properties of carbon-graphite coatings with different granulometric and chemical composition were analyzed for the first time. Multifunctional composite coatings for electromagnetic shielding can have a wide range of applications such as following: in the military and medical practice, specialized protective clothing, in screens for shielding equipment, rooms, and others.