София 22 - 24 October 2024
HARDNESS INFLUENCE ON THE ADHESION OF THIN PROTECTIVE COATINGS FOR AEROSPACE APPLICATIONS
Abstract The Ti-Al-V alloy is mostly used in the aerospace and automobile industries as light material with good strength and elasticity. However, it shows some drawbacks, such as high friction coefficient, especially at elevated temperatures, as well as fast oxidation and deterioration of its chemical and crystal structure. Thus, it turn improper it use, where the surface properties are of importance. The present study aims to cover this alloy with a protective layer of thickness up to 3 microns with especially pronounced compositional gradient character in order to minimize these drawbacks. The chosen protective coatings are based on Ti-carbo-nitride multilayers, providing outstanding hardness exceeding 30 GPa, while keeping low friction coefficient and excellent adhesion properties even at extreme conditions. The coatings were deposited by Physical Vapor Deposition (PVD). The adhesion is an important quality and the present study shows that near the interface, the both Young modules at the adjacent materials should be close.
P. Tabakova1, A. Petrova1, G. Avdeev2, L. Slavov3, K. Grigorov1
1Space Research and Technology Institute, Bulgarian Academy of Sciences
2Institute of Physical Chemistry “Rostislaw Kaischew”, 3Institute of Electronics “Acad. Emil Djakov”
BULGARIAN ACADEMY OF SCIENCES
Keywords: Protective multilayers, adhesion, hardness, wettability, friction coefficient
Experimental data
Polar SE component dependence of the film hardness
at different depths. A – on the Ti6Al4V surface (substrate),
B1 – close to the substrate, B0 – on the TiCN surface
For practical use, the surface energies of samples A, B1 and B0 are estimated using an approach for the work of adhesion Wa written by Owens, Wendt, Rabel and Kaelble method (WORK) for two or more liquids, where the surface free energy components of the solid become linear regression coefficients. Based on two different liquids and their dispersive and polar components γp and the measured contact angles θ, the SE (γ) of the solid is calculated by the following relation:
Two cubic phases of TiCN thin film
by X-ray diffraction
C0.7N0.3Ti
Reference code: 00-042-1489
4.29 Å x, 36.2 (111), 42.02 (200)
C0.2N0.8Ti
Reference code: 01-076-2484
4.24 Å x, 36.6 (111), 42.5 (200), 5.35 g/cm3
Schematic representation of the gradient multilayer structure
Scratch test for TiCN multilayers and base sample TiAlV
Microhardness HV for TiCN and base TiAlV
TiCN coatings with gradient structure with enhanced adhesion were deposited on an industrial type Ti6Al4V light alloy (substrate) in order to gain better hardness and low friction. Another goal, successfully achieved, were to prevent the substrate from oxidation, which occur mostly in high temperature processing regime. Due to the coating application, the hardness rises from 4 GPa (Ti6Al4V) to 40 GPa (+TiCN), while the friction dropped to 0.22 from 0.46 for the Ti6Al4V solely.
Conclusion
CoF µ for TiCN multilayers