Abstract
The paper presents the results of investigating the properties of metal and ceramic coatings deposited on the steel or the aluminium substrates by using a multi-chamber gas-dynamic accelerator. The multi-chamber gas-dynamic accelerator (MCDS) has replaceable nozzles and operates with a fuel mixture of low-pressure gases – propane (30 %) + butane (70 %) – oxygen – air. The velocity of the frontal area of the cloud of the Al2O3 powder with particle sizes of 5.6 – 22.5 μm at a nozzle length of 500 mm is 1300 ± 200 m/s. MCDS with a nozzle length of 500 mm provides the conditions for formation of a dense ceramic layer having hardness of 1320 ± 25 HV0.3 and porosity of less than 1 %. Productivity of the technology is 0.72 kg/h at a deposition efficiency - 65 %, flow rate of oxygen equal to 7.7 m3/h, and flow rate of propane + butane equal to 1.3 m3/h. High adhesion of the ceramic layer to the substrate is provided by the transition layer up to 15 μm thick.MCDS allows form Nano-crystalline coating of the titanium or nickel based alloy powders. The dense layer of lamellas and deformed particles of powder is formed on the sample surface. Lamellas consist of Nano-crystalline grains size of 30 – 100 nm. Scratch-test has shown that the coatings are plastic and have high adhesive and cohesive strength.
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