VACUUM SYSTEM FOR COATING PARTS OF ROCKET AND SPACE EQUIPMENT

Abstract

A vertical type vacuum plant was created for applying coatings using the ion-plasma deposition method to the inner surface of hollow products with a diameter of up to 200 mm and a length of up to 1000 mm. The plant includes: a vacuum chamber with a vacuum system, an evaporator with a magnetic system, a power supply and control system, a cooling system. Radial evaporation cathode of tubular shape with controlled arc is used. Inside the cathode is a magnetic system that controls the movement of cathode spots on its surface. Permanent magnets create arched magnetic fields that hold the position of the discharge track in the tangential direction. The trajectory of the movement of the cathode spots has the form of an ellipse stretched along the cathode. For uniform spraying of the cathode surface, the track moves in two directions: around the circumference of the cathode surface and along its length. A mechanism for moving the magnetic system is mounted on the cover of the vacuum chamber. The product to be coated is mounted inside the vacuum chamber in a vertical position thanks to the removable top cover. The necessary rarefaction of the atmosphere (vacuum) is achieved with the help of two vacuum pumps. Coating materials are traditional Сr and Ni-Cr alloys. A feature of the coating structure is presented: the formation of a combination of solid condensed and soft droplet phases. The droplet phase is a part of the evaporator material with several times lower hardness compared to the nitrided condensed phase. The distribution of the soft phase in a strong coating prevents its brittleness, which is important for thick coatings. The disadvantage of the vacuum-arc deposition process is the heating of the part to a temperature of 380-450 °C. To exclude the softening of the main metal of the combustion chamber and nozzle, it is recommended to use bronze alloys with a recrystallization temperature of at least 500 °C.