Self-Brazed Abrasive Preforms for Turbine Tip Wear Resistance
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Solution Overview
Problem
Existing methods for applying abrasive coatings to gas turbine engine components, such as turbine blades, face challenges in achieving optimal wear-in and minimizing clearance between rotating parts, leading to inefficiencies due to inadequate wear resistance and environmental protection.
Innovation Solution
A method involving the application of a self-braze material with embedded abrasive particles, specifically cubic boron nitride, to the substrate, which includes a mixture of low and high melting point alloys, allowing for secure bonding and environmental protection, and optionally a cast intermediate layer for dimensional restoration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If direct plating or spraying methods are used to apply abrasive to blade tips, then the abrasive coating can be applied to the substrate, but the wear resistance and environmental protection are inadequate
Solution Approach 1:
The patent applies composite materials by combining abrasive particles (such as cubic boron nitride) with a self-braze matrix material to create a composite coating structure. This composite approach provides both the hardness needed for wear resistance and the bonding capabilities for secure attachment to the substrate, resolving the contradiction between wear resistance and manufacturing quality.
Solution Approach 2:
The patent changes the physical and chemical parameters of the coating material by using a self-braze material with specific compositional ranges (e.g., nickel 5-20%, cobalt 10-30%, chromium 15-35%, aluminum 5-15%) and controlling the braze temperature (2000-2500°F). These parameter changes enable the coating to achieve both adequate wear resistance and secure bonding to the substrate.
2Reliability
If conventional braze materials are used, then the abrasive can be bonded to the substrate, but oxidation and corrosion resistance are insufficient
Solution Approach 1:
The self-braze material itself is a composite material containing multiple alloying elements (nickel, cobalt, chromium, aluminum, silicon, boron, tantalum, tungsten, rhenium, molybdenum) in specific proportions. This composite composition provides both the bonding functionality and the oxidation/corrosion resistance, eliminating the need for separate protective layers and reducing overall device complexity.
Solution Approach 2:
The self-braze material performs multiple functions simultaneously: it acts as the bonding agent to attach the abrasive to the substrate, provides environmental protection through oxidation and corrosion resistance, and maintains structural integrity at high temperatures. This multi-functionality resolves the contradiction between reliability and device complexity.
3Productivity
If abrasive coating is applied to minimize clearance between blade tips and BOAS segments, then radial clearance is reduced and efficiency increases, but the coating must withstand high stress and thermal conditions
Solution Approach 1:
The abrasive particles (such as cubic boron nitride with Mohs hardness 9.5-10) embedded in the self-braze matrix create a composite structure where the abrasive provides hardness for wear resistance and the matrix provides toughness and thermal stability. This composite structure enables the coating to withstand the high stress and thermal conditions while maintaining the reduced clearance needed for engine efficiency.
Solution Approach 2:
The patent optimizes the compositional parameters of the self-braze material (e.g., chromium content 15-35% for oxidation resistance, nickel 5-20% and cobalt 10-30% for high-temperature strength) and processing parameters (braze temperature 2000-2500°F, holding time 5-30 minutes) to achieve a coating that can endure high stress and thermal conditions while maintaining durability.
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
This approach enhances wear resistance, minimizes clearance, and extends the operational life of turbine components by providing improved oxidation and corrosion resistance, leading to increased efficiency and durability.
Implementation Method 1
securing the combination to the substrate
Implementation Method 2
heating to cause the self-braze material to braze to the substrate
Implementation Method 3
an abrasive embedded in the self-braze material; specifically cubic boron nitride
Implementation Method 4
providing improved oxidation and corrosion resistance
Implementation Method 5
providing improved oxidation and corrosion resistance
Data Source
AI summary
A method for applying an abrasive comprises: applying, to a substrate, the integral combination of: a self-braze material; and an abrasive embedded in the self-braze material; and securing the combination to the substrate.