Turbine Blade Tip PVD Coatings for Abradable Rub Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Turbine blades experience significant wear damage due to contact with abradable substrates like CoNiCrAlY-boron nitride, NiCrAl bentonite, and NiCrAl-boron nitride coatings during rub incursion events, leading to premature blade tip wear and potential engine damage, especially under conditions of high thermal expansion, rapid loading changes, and inefficient cutting forces.
Innovation Solution
Application of physically vapor deposited (PVD) thin film hard coatings on blade tips, such as titanium nitride (TiN), titanium aluminum nitride (TiAlN), and chromium nitride (CrN), which provide exceptional wear resistance and adhesion without the need for surface preparation, allowing for thinner coatings that reduce wear and oxidation issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If blade tips are made to contact abradable substrates to minimize tip gap, then gas flow leakage is reduced, but blade tip wear increases significantly
Solution Approach 1:
The blade tip is equipped with a localized abrasive coating layer having different properties than the blade substrate. This coating layer is specifically designed to be harder and more wear-resistant than the abradable substrate, while the rest of the blade maintains its original properties. This resolves the contradiction by protecting only the contact region (tip) while maintaining the overall blade functionality.
Solution Approach 2:
The abrasive coating is applied to the blade tip before operation, preparing it in advance for contact with the abradable substrate. This preliminary protection allows the blade to immediately engage the abradable material without suffering wear damage, enabling the tip gap to be minimized from the start of operation.
2Reliability
If thicker coatings are applied to blade tips for wear protection, then wear resistance improves, but coating thickness tolerances become difficult to control
Solution Approach 1:
The invention changes the material parameters of the coating layer, selecting materials with specific hardness and wear resistance properties that exceed those of the abradable substrate. By optimizing the coating material composition and applying thin layers (5-50 micrometers), the invention achieves superior wear protection while maintaining precise thickness control that is difficult to obtain with thicker coatings.
3Reliability
If PVD coatings are applied to blade tips, then wear resistance against abradable substrates improves, but oxidation resistance at high temperatures may be compromised
Solution Approach 1:
The invention uses composite material systems where the abrasive coating layer is applied over a metallic bond coat layer. The bond coat provides oxidation and corrosion resistance at high temperatures, while the abrasive coating layer provides wear resistance against the abradable substrate. This composite structure resolves the contradiction by assigning different protective functions to different layers.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The PVD coatings significantly reduce blade tip wear and eliminate damage under various incursion conditions, enabling the use of harder abradable materials like thermally sprayed porous zirconia oxide coatings without damaging the blade tips, while maintaining oxidation resistance and improving surface finish.
Implementation Method 1
Application of physically vapor deposited (PVD) thin film hard coatings on blade tips
Data Source
AI summary
The present invention discloses a turbine engine with at least a high pressure and a low pressure turbine section comprising a casing and at least one turbine blade rotatably mounted within the casing wherein at least part of the inner surface of the casing is covered with shrouds as abradables to provide clearance control between the inner surface and the tip of the at least one blade and wherein the tip of the blade is coated with a hard PVD coating, characterized in that the shroud material of at least the high pressure and/or the low pressure section comprises a porous ceramic based material and the hard PVD coating on the tip of the blade essentially consists of a droplet free nitride coating.