Wear Resistant Airfoil Tip Coating for Gas Turbine Sealing
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Solution Overview
Problem
The existing methods for configuring airfoil tips and casing seals in turbine engines to minimize gas leakage are costly and time-consuming, particularly during reconditioning, as they require abrasive materials like cubic boron nitride.
Innovation Solution
A wear-resistant coating with metal boride compounds, such as M3B4, is applied to the airfoil tips, providing a hardness of 1500 to 2500 HV 0.05 g and a thickness of less than 10 mils (254 micrometers), which includes forming the coating on the base metal surface using boronizing processes like gaseous, liquid, or plasma-assisted chemical vapor deposition, to enhance the sealing efficiency without metal transfer during sliding contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If abrasive material such as cubic boron nitride is applied to airfoil tips, then wear resistance is improved, but manufacturing cost and time increase
Solution Approach 1:
The patent changes the material parameters by using metal boride compounds (such as TiB2, ZrB2, HfB2) instead of traditional cubic boron nitride. These boride compounds can be applied as coatings with thickness of 0.001 to 0.006 inches, providing comparable wear resistance but with simplified application processes that reduce time and cost, particularly during reconditioning operations
Solution Approach 2:
The invention creates a composite structure by forming metal boride compounds on the airfoil tip surface through boronizing processes. This composite material system combines the base metal with boride compounds to achieve high wear resistance and cutting ability against abradable seals, eliminating the need for expensive cubic boron nitride while maintaining performance
2Strength
If abrasive material is applied to airfoil tips, then cutting ability is improved, but manufacturing cost increases
Solution Approach 1:
The patent modifies the material composition by using metal boride compounds that provide sufficient cutting ability to abrade the seal material. The boride compounds form a hard coating that maintains cutting effectiveness while being more cost-effective than cubic boron nitride, reducing manufacturing costs particularly during reconditioning
Solution Approach 2:
The invention employs a more economical material solution using metal boride coatings that can be applied at lower cost. While the coating has limited thickness (0.001 to 0.006 inches), it provides sufficient service life and cutting ability for the intended application, offering a cost-effective alternative to expensive cubic boron nitride
3Loss of energy
If airfoil tips contact seal during operation, then gas leakage is minimized, but metal transfer occurs
Solution Approach 1:
The patent applies a localized treatment to the airfoil tip surface by forming metal boride compounds only on the contacting surface through boronizing processes. This localized application creates a hard, non-transferring coating exactly where contact with the seal occurs, preventing metal transfer while maintaining the sealing function that minimizes gas leakage
Solution Approach 2:
The invention creates a composite surface structure where metal boride compounds are formed on the airfoil tip surface. This composite material provides a non-stick, non-transferring surface that prevents metal transfer to the seal during contact operation, while still enabling the contact sealing mechanism to minimize gas leakage effectively
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 wear-resistant coating effectively reduces gas leakage by improving the cutting ability of the airfoil tips and preventing metal transfer, thereby increasing engine efficiency and reducing reconditioning costs.
Implementation Method 1
The wear resistant coating includes metal boride compounds and has a thickness less than or equal to 10 mils (254 micrometers). The wear resistant coating is formed in a base metal surface of the airfoil and the metal boride compounds include M3B4
Implementation Method 2
the wear resistant coating is formed by surrounding the airfoil with a source of metal atoms followed by surrounding the airfoil with a source of boron atoms
Implementation Method 3
the wear resistant coating is formed on the base metal surface using boronizing processes like gaseous, liquid, or plasma-assisted chemical vapor deposition
Data Source
AI summary
A gas turbine engine includes an engine static structure extending circumferentially about an engine centerline axis; a compressor section, a combustor section, and a turbine section within the engine static structure. At least one of the compressor section and the turbine section includes at least one airfoil and at least one seal member adjacent to the at least one airfoil. A tip of the at least one airfoil is metal having a wear resistant coating and the at least one seal member is coated with an abradable coating. The wear resistant coating is formed as a layer in a base metal surface of the airfoil, has a thickness less than or equal to 10 mils (254 micrometers) and includes metal boride compounds.