Gold Coated Titanium Aluminide Substrate Corrosion Protection
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Solution Overview
Problem
Titanium aluminides face significant challenges in resisting corrosion, particularly in environments with oxygen, sodium sulphate, and halogenated compounds, due to self-perpetuating corrosion mechanisms and lack of a stable oxide layer, which damages components like aircraft engine parts.
Innovation Solution
A process involving the deposition of a gold coating on titanium aluminide substrates, followed by controlled annealing to form a protective TiAlAu3 composition, which enhances resistance to oxidation and corrosion while maintaining mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a titanium aluminide alloy is used for high temperature applications, then good mechanical properties and low density are achieved, but resistance to oxidation and corrosion deteriorates significantly above 700°C
Solution Approach 1:
The patent applies a coating of gold (a noble metal) onto the titanium aluminide alloy surface, creating a composite structure where the base alloy provides mechanical strength and low density, while the gold coating provides oxidation and corrosion resistance at high temperatures
Solution Approach 2:
The gold coating creates an inert protective environment on the alloy surface, preventing direct contact between the reactive titanium aluminide and the corrosive atmosphere containing oxygen, sulphur compounds, and halogenated compounds
2Temperature
If the alloy operates in a halogenated environment above 600°C, then functional performance is maintained, but self-perpetuating corrosion mechanisms cause severe damage
Solution Approach 1:
The gold coating acts as an intermediary barrier between the alloy and the halogenated environment, preventing the formation of volatile aluminium halides that drive the self-perpetuating corrosion mechanism while allowing the alloy to operate at elevated temperatures
3Temperature
If oxidation occurs above 700°C, then thermal exposure is tolerated, but no stable sealing oxide layer forms and kinetic oxidation increases rapidly
Solution Approach 1:
The gold coating serves as a sacrificial protective layer that prevents direct oxidation of the titanium aluminide alloy, forming a stable protective barrier instead of the unstable complex oxide layers that would form on the bare alloy surface at high temperatures
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 gold coating significantly improves the alloy's resistance to oxidation and corrosion, remaining intact during severe testing conditions, including cyclic oxidation and halogenated corrosion, while slightly preserving mechanical properties.
Implementation Method 1
subject the substrate thus equipped with the gold coating to annealing in controlled conditions in order to bring about limited diffusion of the gold into the surface to be protected
Implementation Method 2
subject the substrate thus equipped with the gold coating to annealing in controlled conditions
Data Source
AI summary
The method according to the invention comprises the following operations:a) prepare a substrated formed of the said intermetallic alloy;b) deposit a coating of gold on the surface to be protected of the substrate; andc) subject the substrate thus equipped with the gold coating to annealing in controlled conditions in order to bring about limited diffusion of the gold into the surface to be protected. The invention is applicable in particular to parts of gas turbines, e.g. parts of aircraft engines.