General principles for controlling the quality of gas-flame coatings while doing component overhaul
Gas-flame spraying is one of perspective technological methods of applying recovery and hardening coatings. Lack of a quality-control system for gas-flame coatings are impeding widespread introduction of this way of spraying. This method of component restoration does not require purchasing the expensive equipment and, consequently, is suitable for the majority of enterprises, even if they are of a small scale. To develop the principles for controlling the quality of gas-flame coatings, the factors are necessary to be considered, influencing the coating quality. These factors can be divided into two groups. The first group contains the factors, defining the parameters of the gas-flame spraying process such as composition and consumption of the gas-flame mixture, properties of the sprayed material, design of a gas-flame torch, speed and temperature of the gas-flame stream and sprayed particles. The second group contains hardness and roughness of the sprayed surface, distance of spraying, foundation temperature, movement speed of the sprayed surface in relation to a gas-flame torch, refrigerating conditions for the sprayed coating, additional impacts on the sprayed component and the coating. As output parameters the coupling durability between coating and the foundation, the efficiency of the applied material and the coating porosity are usually accepted.