Heat-Resistant CCCM Coatings for Aerospace Applications
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Vol. 61, No. 1, May, 2020
HEAT-RESISTANT CCCM COATINGS FOR AEROSPACE APPLICATIONS D. Yu. Sinitsyn,1,3 V. N. Anikin,2 S. A. Yeremin,1 A. G. Yudin,1 and K. O. Chuprunov1 Translated from Novye Ogneupory, No. 2, pp. 65 – 73, February, 2020.
Original article submitted October 26, 2019. The paper discusses the layered heat-resistant coatings for aerospace applications obtained by atmospheric plasma spraying (APS) technique. The following coating material compositions were selected, wt. %: 1 — 20(ZrO2–8Y2O3) + 80MoSi2; 2 — 10(ZrO2–8Y2O3) + 90MoSi2. As the sublayer thickness decreases and MoSi2 content increases, the strength of the coated sample becomes higher. It was established that the coating composition 2 completely satisfies the heat resistance test requirements, and presumably undergoes plastic deformation. Keywords: atmospheric plasma spraying, carbon-carbon composite material (CCCM), heat resistance.
ity and tensile strength, and inversely proportional to the Young’s modulus and TCLE. In addition, from the physical and mechanical point of view, heat resistance can be improved by using the composite coating components forming glass phases during operation, which are capable of healing the resulting cracks, as well as glass films reflecting the heat flux. To achieve the set goals, multi-layer protective coatings made of refractory compounds with relatively high thermal conductivity and relatively low TCLE values were used in this study. Specifically, the coatings based on refractory zirconium and hafnium oxides were used (TCLE ~10 ´ 10–6 deg–1). For ZrO2 characterized by high bending and compression strength, the phase composition is important, since both zirconium and zirconium oxide are polymorphic materials having three phases: a stable monoclinic a-phase, metastable tetragonal b-phase, and unstable cubic g-phase. The tetragonal phase is the strongest and is characterized by the highest impact toughness. This phase can be achieved by partially stabilizing ZrO2 with 2 – 3 wt.% of Y2O3, which results in ceramics consisting of small metastable tetragonal particles. As the percentage of tetragonal phase increases, the transformation strengthening improves [5, 6]. During plasma deposition, as a result of high precipitation rates, the coating of the ZrO2–Y2O3 system contains tetragonal phase, which is highly desirable for plasma-deposited coatings, since the a ® b transformation does not occur
INTRODUCTION Carbon-carbon composite materials (CCCMs) are 2D-composites having a pyrocarbon matrix reinforced with carbon fibers. Recently, CCCMs have been used extensively as individual components of aerospace vehicles, specifically, in parts and nozzles of the rocket gas turbine engines (GTE), leading edges of the lifting surfaces, and skin of hypersonic aircraft, because of their ability to satisfy the ever-increasing demands. This is achieved due to the fact that such materials possess high specific strength and rigidity at low density, modulus of elasticity (12.8 GPa), and TCLE (
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