Polymer Coating for Gas Turbine Blade Root Anti-Fretting
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Solution Overview
Problem
Current metallic coatings for rotor blades in gas turbines and compressors are prone to adhesion/cold welding with the rotor disk, leading to fretting and fretting fatigue, making blade removal difficult and costly, and are challenging to repair.
Innovation Solution
A polymer coating, preferably based on fluoropolymers with embedded solid lubricants, is applied to the blade roots and rotor disk slots to reduce energy input during movement, prevent adhesion/cold welding, and alleviate fretting fatigue, allowing for easier installation, operation, and repair.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metallic coatings (CuNiIn, NiTiCr) are applied to reduce fretting, then fretting and fretting fatigue are reduced, but adhesion/cold welding occurs between the coating and rotor disk, making blade removal difficult
Solution Approach 1:
A polymer coating layer is introduced as an intermediary between the metallic blade root and the rotor disk slot. This polymer layer prevents direct metal-to-metal contact and adhesion while maintaining fretting protection, enabling easy blade removal without damaging the underlying metallic structures
Solution Approach 2:
The solution uses a composite coating system where a polymer material is applied over or instead of traditional metallic coatings. The polymer provides both fretting protection and anti-adhesion properties, combining the benefits of friction reduction with easy removability
2Loss of energy
If metallic coatings are used to reduce fretting, then energy input during relative movement is reduced, but similar metallic materials are in contact which promotes adhesion and cold welding
Solution Approach 1:
The material parameter of the coating is changed from metallic to polymer. This fundamental material parameter change alters both the friction characteristics (maintaining low energy input) and the adhesion characteristics (preventing cold welding between dissimilar materials)
Solution Approach 2:
The polymer coating creates a homogeneous non-metallic layer that separates the two metallic components, ensuring that no similar metallic materials are in direct contact, thereby eliminating the conditions for adhesion and cold welding
3Reliability
If traditional metallic coatings are applied, then fretting protection is achieved, but damage to the coatings can be repaired only with great difficulty
Solution Approach 1:
The polymer coating is designed to be replaceable and repairable with simple applications. If damaged, the polymer coating can be easily removed and reapplied without complex repair procedures, treating the coating as a consumable protective layer that simplifies maintenance
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 polymer coating provides a long-term separating effect, reduces localized stress, is cost-effective, and enables on-site repair of rotor blades, while improving load-bearing behavior and damping properties, though limited by operational temperature constraints.
Implementation Method 1
The input of energy due to relative movement is reduced by a low coefficient of friction between the rotor blade and rotor disk slot components
Implementation Method 2
A polymer coating, preferably based on fluoropolymers with embedded solid lubricants, is applied to the blade roots and rotor disk slots to reduce energy input during movement, prevent adhesion/cold welding
Implementation Method 3
improving load-bearing behavior and damping properties
Data Source
AI summary
The use of a polymer coating in the carrying flank region minimizes damages. Moreover, a long-term separating effect between the components, e.g. rotor blade and rotor disk, is ensured. According to the embodiments, the rotor disk groove can alternatively also be coated in whole or in part.