Effect of Production Parameters on the Structure of the Outer Ceramic Layer in Two-Layer Metal - Ceramic Coatings Prepared by Electron-Beam Deposition in One Production Cycle

Abstract

The effect of production parameters for electron-beam deposition of two-layer metal − ceramic coatings in one production cycle on the structure and phase composition of the outer ceramic layer based on zirconium oxide stabilized with yttrium oxide is studied. It is shown that it is possible to obtain metal − ceramic coatings with the required functional properties in one production cycle.Two-layer protective metal − ceramic coatings are used extensively in engine building in order to protect gas turbine blades [1][2][3]. It is well known [1] that in order to deposit the inner metal layer there is use of MCrAlY (where M is nickel, cobalt, iron), and for the outer ceramic layer there is use of zirconium dioxide ZrO 2 stabilized with yttrium oxide Y 2 O 3 (Yttrium Stabilized Zirconium Oxide, YSZ). The life of blades with this two-layer coating is governed to a considerable extent by deposition parameters. In spite of the extensive results of research devoted to this question [1][2][3][4][5][6][7] there are no published clear recommendations for deposition of these coatings.Normally two-stage technology is used in order to form two-layer metal − ceramic coating on turbine blades. The inner metal layer is applied to an article by means of vacuum plasma spray (VPS); air plasma spray (APS) or electron-beam physical vapor deposition (EB-PVD). A method used in the production cycle for two-layer coating deposition is shot-blasting treatment of the surface of the metal layer followed by annealing in a vacuum furnace with the aim of "healing" structural defects in the deposited layer [3]. Sometimes in order to obtain the required roughness before deposition of the outer ceramic layer the surface of the inner metal layer is subjected to hydraulic-abrasive treatment by a water emulsion of clay [4] and only then is the outer layer applied by one of the methods mentioned.Until recently in the economically developed European countries and the USA the preferred method for applying metal − ceramic protective coatings has remained plasma deposition. In some of the leading engine building firms of the world, in particular "Pratt and Whitney," there is use of a combined method for preparing two-layer coatings. The inner MCrAlY coating is applied by plasma deposition and the outer ceramic layer is applied by electronbeam deposition. Use of different equipment complicates the production process and makes it more expensive. A fundamental solution of the problem is deposition of a two-layer metal − ceramic coating in one type of equipment in one production cycle. We note that the effect of using two-layer metal − ceramic coatings depends to a considerable degree on the perfection of the production processes. It is considered [1][2][3]8] that the electron-beam method for depositing the outer ceramic layer has certain advantages compared with plasma deposition, i.e. increased cyclic endurance in thermal cycling for the ceramic layer obtained.Scientific-Production Enterprise "GEKONT," Vinnitsa, Ukraine.

Microcracking in electron beam deposited scandia-stabilised zirconia electrolyte

“…An electron beam is directed at a target pellet, in order to ionize and melt the target material, which is then accelerated in an electrical field and deposits on the specimen to be coated. The process is rather slow but results in a very precise control of layer thickness and, when applied expertly, delivers very thin, dense coatings, as needed for intermediate temperature electrolytes [21]. These thin layers again reduce the overall resistance of the electrolyte and further support the trend towards higher power density/lower operating temperatures.…”

Powder metallurgy industry and managerial economics

“…This study logically continues the research conducted at the Research and Development Enterprise Gekont (Vinnitsa) and intended to develop an industrial technology for depositing thermalbarrier coatings on gas turbine blades [4][5][6].…”

“…A thermal-barrier coating may have excellent characteristics and proper adhesion with the metal base only if there is a layer of a multicomponent MCrAlY alloy (where M = Ni, Co, Fe, or their combinations) preliminary placed on the product. To apply thermal coatings on gas turbine blades, a two-stage process is widely employed: (i) plasma deposition of a metal high-temperature binding MCrAlY sublayer and (ii) subsequent deposition of ceramics (plasma or electron-beam vapor deposition).Nevertheless, the development of new, more reliable and efficient one-stage processes for applying protective coatings is underway [4][5][6][7].The paper [6] examines the effect of the deposition parameters on the structure and properties of the resulting TBCs. However, some important aspects have not been covered, namely: the effect of high-temperature annealing, texture features, phase composition, and distribution of chemical elements across the TBCs applied with the proposed technology [6].…”

“…However, some important aspects have not been covered, namely: the effect of high-temperature annealing, texture features, phase composition, and distribution of chemical elements across the TBCs applied with the proposed technology [6].…”

“…Nevertheless, the development of new, more reliable and efficient one-stage processes for applying protective coatings is underway [4][5][6][7].…”