2-LAYER AND 3-LAYER COATINGS PRODUCED BY DEPOSITION IN VACUUM FOR GAS-TURBINE BLADE PROTECTION

This paper deals with the microstructure and properties of oxidation-r esistant metal/ceramic coatings produced by the electron beam evaporat ion of M-Cr-Al-Y alloys and zirconia partially stabilized by yttria. T he effect of thermophysical conditions of deposition on the properties of the condensed zirconia and protective coatings is shown. The resul ts of furnace tests in air and gas turbine fuel ash showed that the do uble-layer metal/ceramic coatings increase the oxidation and corrosion resistance of nickel alloys at 750-1000 degrees C. Burner tests of sp ecimens and blade models with Co-Cr-Al-Y/ZrO2, coatings in a gas strea m showed that the metallic coatings possess higher thermal fatigue res istance due to the deposition of the ceramic layer of 50-120 mu m thic kness. The relationship between the thermal cyclic life and multicycle fatigue resistance of alloys with vacuum-deposited metal/ceramic coat ings is expressed by a curve with a maximum corresponding to ZrO2-Y2O3 90-120 mu m thick. Potential improvement of M-Cr-Al-Y/ZrO2, coatings is increased in service when a ductile interlayer is inserted between the oxidation-resistant layer and base metal. Data are given about the dependence of the mechanical properties of heat-resistant nickel allo ys on ZrO2-Y2O3 coatings of 60-150 mu m thickness.