Improving the quality of thermal spray coatings for blades of gas turbines

Abstract

Methods of controlling the quality of nickel and cobalt based protective coatings on a nickel alloy substrate by the gas-plasma method using a plasma torch with a power of 55 kW are considered. The dependences of some operational characteristics of the studied coatings on the most significant technological parameters were obtained: the speed of the plasma torch and the angle of supply of the gas jet to the substrate. It was shown that varying these parameters allows controlling the amount of oxidized particles, pores and voids in the coating, the content of which determines the cohesive and adhesive properties of the protective layer, which in turn serves as quality criteria for the protective coating. It was found that nickel-based coatings, due to their better plastic deformation ability, have greater cohesive strength than cobalt-based coatings. It was found that the thermal treatment of thermal spray coatings in vacuum provides some compaction of the protective layer and relatively weakly affects its adhesion and cohesion. It was also shown that heat treatment of the studied coatings in the open air is impractical due to the significant oxidation of individual structural components in the sprayed layer and a corresponding decrease in the cohesive properties of the coating as a whole.