Cathodic Arc Target Grain Boundary Strengthening
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Solution Overview
Problem
Cathodic arc deposition of alloy bond coats for turbine engine components faces challenges such as intergranular separation and fracture due to high temperature gradients and internal stresses, leading to wasteful target failure during high deposition rates, which affects the quality and throughput of the protective coatings.
Innovation Solution
Incorporating grain boundary strengthening alloy additions, specifically 2 to 50 ppm Ce, into the base alloys like NiCrAlY, CoCrAlY, and their platinum-modified variants, to form targets that minimize intergranular separation and enhance the durability of cathodic arc targets during deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high deposition rates are used in cathodic arc deposition, then productivity is improved, but intergranular separation and target fracture occur due to temperature gradients and internal stresses
Solution Approach 1:
The invention changes the chemical composition parameter of the target material by adding grain boundary strengthening alloying elements (such as B, Si, C, or combinations) to modify the microstructural properties and enhance resistance to thermal stress and intergranular separation during high-rate deposition
Solution Approach 2:
The invention creates a composite alloy system by combining base metals (Ni, Co, Fe, Cr, Al, Y) with grain boundary strengthening additions, forming a multi-element alloy that leverages synergistic effects to simultaneously achieve oxidation resistance and thermal stress resistance
2Ease of manufacture
If conventional base alloys are used without grain boundary strengthening additions, then manufacturing simplicity is maintained, but intergranular separation occurs during cathodic arc deposition
Solution Approach 1:
The invention modifies the compositional parameters of conventional base alloys by incorporating small amounts of grain boundary strengthening elements, which fundamentally changes the material's resistance to intergranular separation while maintaining compatibility with existing cathodic arc deposition processes
3Reliability
If platinum is added to base alloys for oxidation resistance, then protection against extreme conditions is improved, but cost and manufacturing complexity increase
Solution Approach 1:
The invention applies local quality enhancement by concentrating grain boundary strengthening elements at intergranular regions through controlled addition, providing localized reinforcement where thermal stress and oxidation resistance are most critical, rather than uniformly distributing all alloying elements throughout the bulk material
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 addition of cerium as a grain boundary strengthening element delays or prevents high-temperature grain boundary separation and fracture, resulting in improved target stability and increased product throughput by reducing the likelihood of catastrophic failure during cathodic arc deposition.
Implementation Method 1
techniques (e.g. plasma spraying, cathodic arc plasma deposition)
Implementation Method 2
The energy deposited by the arc at a cathode spot is intense; on the order of 10 5 watts/cm 2. The intensity of the energy raises the local temperature of the cathode spot to approximately equal that of the boiling point of the cathode material
Data Source
AI summary
A method of forming targets for cathodic arc deposition of alloy bond coats for turbine engines components consists of melting a base alloy containing aluminum and other metals, adding grain boundary strengthening alloy additions, and casting the melt to form a cylindrical billet that is subsequently sectioned into puck shaped targets. The grain boundary strengthening additions minimize intergranular fracture of the targets during high current operation of the arc coating process.