SEM, 2019, #3, 45-54 pages
Journal Современная электрометаллургия
Publisher International Association «Welding»
ISSN 2415-8445 (print)
Issue № 3, 2019 (September)
Effect of condensed multilayer protective coatings on fatigue resistance of VT6 alloy samples
K.Yu. Yakovchuk1, A.V. Mykytchyk1, Yu.E. Rudoy1, Yu.F. Lugovskoy2
State-Run Enterprise «International Center for Electron Beam Technologies
of E.O. Paton Electric Welding Institute, NASU».
68 Gorky (Antonovich) Str. 03150, Kyiv, Ukraine. E-mail: firstname.lastname@example.org
Frantsevich Institute for Problems of Materials Sciences NASU.
3 Krzhizhanovsky str., 03680, Kyiv, Ukraine. E-mail: email@example.com
The effect of multilayer damping and erosion-resistant functional coatings 28…96 μm thick on high-cycle fatigue strength of VT6 alloy samples is considered. Coatings were applied by electron beam physical vapor deposition (EB-PVD) on VT6 titanium alloy substrates. Room-temperature high-cycle fatigue tests were conducted by exciting resonant bending oscillations of the first (non-destructive stresses) and second forms of oscillations in the sample at frequencies of 0.4 and 2.0 kHz on the basis of 107
cycles, respectively. It was found that deposition of single-layer B4
C coatings on VT6 alloy samples is impractical due to poor adhesion of the coating (bending angle was 4°). If inner bonding layer (Ti, Ag, Hf 1...3, 2.5...15.0, 1...2 μm thick, respectively) was used, it was possible to increase the adhesion of the coating (bending angle was 20...25°), while the endurance limit decreased by 29...33 % compared with an uncoated alloy. It was demonstrated that the inner bonding layer (Cu or AgCu) provides high adhesion (the bending angle reached 36…48°). However, the endurance limit decreased by 33…49 % due to rapid penetration of the fatigue crack through this inner bonding layer into the VT6 alloy. Deposition of inner bonding multilayer (coatings of Hf/Ti/Hf/Ti/Cr or AgСu/Ti/AgCu/Ti/AgCu/B4
C type) with an optimal ratio of individual layer thicknesses ensures endurance limit at the level of 73...80 % of uncoated samples. Furthermore, it was found that multilayer Hf/Ag/Ni/Cr damping coatings 52 μm thick ensure a decrease of the amplitude of oscillations (effective stresses in the sample) by 23...56 % as compared to uncoated samples. The tests were carried out using the same power supplied from testing rig to coated and uncoated samples for oscillation excitation. Therefore, to evaluate the damping efficiency of various coatings and their effect on high-cycle fatigue of substrate material, it is recommended to conduct vibration tests of samples at the same power supplied for oscillation excitation. Ref. 18, Table 1, Fig. 8.
Key words: alloy; electron beam physical vapor deposition; high-cycle fatigue; protective (functional) coatings; multilayer coatings; fatigue crack; compressor blades
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