The effect of suspension parameters on the properties of the coating obtained by the slip method

Abstract

The development of modern gas turbine engineering imposes increasingly high requirements for the properties of the alloys used, associated with an increase in gas temperature before the turbine. However, the applicable nickel alloys have low heat resistance at high temperatures. The solution to this problem is achieved through the joint use of a heat-resistant alloy that takes loads at high temperatures, and the application of protective coatings to ensure heat resistance. The coating and the heat-resistant alloy form a complex system. Each component of the system performs the primary and secondary functions in the operation, and the system must meet operational requirements. The choice of the applied coating and its application technology are quite complicated, since its structure and thickness depend on many factors, in particular, on the composition of the original components, temperature, and time parameters of its application, etc. This affects the performance of the formed coating under operating conditions. In recent years, slip coating methods specifically formed from aqueous suspensions have been successfully developed abroad and in our country. This method is technically simple and economical. The quality of the coating formed from the aqueous suspension is determined by the percentage of the suspension composition, its rheological and physical properties, compliance with the technology of its application and processing of parts. In order to understand the mechanism of coating formation from the aqueous suspension, it is necessary to imagine the effect of the suspension parameters on the coating properties. The article presents the results of the study carried out by the computational method of the influence of the aqueous suspension parameters on the quality of the coating obtained. The dependence of the coating thickness on the particle sizes of the powders introduced into the suspension is shown. Calculations of the density and thickness of the obtainable coating from the ratio of the solid and liquid phases of the aqueous suspension are presented. It is indicated that in a real suspension, the influence of the aqueous suspension parameters on the coating parameters being formed is more complex than when performing calculations. This is primarily associated with the fact that in a real suspension there are powder particles of various diameters, in particular aluminum. In addition, the interaction of orthophosphoric acid with the introduced oxides of aluminum, silicon, etc., having molecular dispersion, their chemical interaction complicates considering all these factors in calculations. However, the obtained results of the study allow us to assess the influence of the aqueous suspension composition parameters on the technological and service properties of the obtainable coating obtained by the slip method from this suspension.