Machinable Coating for CMC Turbine Blade Mounts
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Solution Overview
Problem
Turbine components in gas turbine engines face challenges in surviving high temperatures due to the products of combustion, and existing materials like ceramic matrix composites (CMCs) require additional protection to prevent wear and chemical reactions at the interfaces with metallic components.
Innovation Solution
A protective coating is applied to the radially outer faces and axial ends of the circumferentially outwardly extending mount portions on the suction and pressure walls of the turbine blades, which are formed from materials such as polymers, metals, or ceramic matrix composites, to enhance wear resistance and prevent chemical reactions, while also improving sealing effectiveness and load transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If CMC materials are used for turbine blades to withstand high temperatures, then temperature resistance is improved, but wear resistance and chemical reaction resistance at metal interfaces deteriorate
Solution Approach 1:
A metallic coating layer is applied to the CMC mount portions to serve as an intermediary between the CMC blade and the metallic turbine disk. This coating layer prevents direct contact and chemical reactions between CMC and metal, while also providing wear resistance at the interface. The coating acts as a protective mediator that allows the CMC blade to maintain its high-temperature resistance while gaining improved interface durability.
2Reliability
If protective coating is applied to mount portions, then wear resistance and chemical reaction resistance are improved, but manufacturing complexity increases
Solution Approach 1:
The protective metallic coating is applied selectively only to the mount portions of the CMC turbine blade that contact the metallic turbine disk, rather than coating the entire blade. This localized application approach maintains wear and chemical reaction resistance at the critical interface while avoiding unnecessary manufacturing complexity and cost associated with full-surface coating.
3Duration of action of stationary object
If CMC materials are used for turbine blades, then high-temperature durability is improved, but sealing effectiveness at interfaces deteriorates
Solution Approach 1:
The metallic coating on the CMC mount portions serves as a mediator that improves sealing effectiveness at the interface with the metallic turbine disk. The coating material can be selected to provide both wear resistance and sealing properties, filling micro-gaps and irregularities at the interface to prevent leakage of hot gases while maintaining the high-temperature durability of the CMC blade.
Data Source
AI summary
A gas turbine engine turbine blade includes a turbine blade body including an inner platform. An airfoil extends radially outwardly of the inner platform. The airfoil has a leading edge and a trailing edge, and a suction wall and a pressure wall. The turbine blade body has mount structure including at least one circumferentially outwardly extending mount portion on a suction wall side and a pressure wall side each having a radially outer face. The turbine blade body is formed of one of a polymer, metal or ceramic matrix composite. There is a protective coating on the radially outer faces of the at least one enlarged mount portions. A gas turbine engine is also disclosed.