Cold Spraying Titanium Aluminide Surface Coatings
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Solution Overview
Problem
Welding or brazing of titanium aluminide (TiAl) components can adversely affect their microstructure and mechanical properties, leading to undesirable duplex structures, reduced strength, and shorter fatigue and creep life.
Innovation Solution
A cold spraying process using a solid feedstock of pre-alloyed titanium aluminide powder is applied to form a refined gamma/alpha2 structure on articles, minimizing heat input and avoiding heat-affected zones, thereby maintaining high strength-to-weight ratio and resistance to high-temperature oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If welding or brazing is used to join TiAl components, then the components can be connected, but the microstructure deteriorates forming undesirable duplex structures with reduced strength and shorter fatigue/creep life
Solution Approach 1:
The invention changes the fundamental parameter of joining temperature from high-temperature welding/brazing (>1150°C) to low-temperature cold spraying (below recrystallization temperature). This parameter change prevents the formation of heat-affected zones and duplex structures, maintaining the refined gamma/alpha2 lamellar microstructure and associated mechanical properties including strength, fatigue life, and creep life.
Solution Approach 2:
The invention replaces the thermal field-based joining method (welding/brazing) with a mechanical field-based method (cold spraying). The cold spray process uses high-velocity particle impact and plastic deformation to achieve metallurgical bonding without significant heat input, thereby avoiding thermal damage to the TiAl microstructure and preserving the refined gamma/alpha2 structure with superior mechanical properties.
2Ease of manufacture
If hot working is performed above 1150°C to process TiAl, then the material can be formed, but the microstructure changes to a duplex structure with equiaxed grains and gamma/alpha2 lamellae, decreasing strength and fatigue/creep life
Solution Approach 1:
The invention changes the processing temperature parameter from high-temperature hot working (>1150°C) to low-temperature cold spraying. This parameter change enables material deposition and forming while preserving the refined gamma/alpha2 lamellar microstructure, avoiding the formation of equiaxed grains and duplex structures that would reduce strength and fatigue/creep life.
3Ease of repair
If welding or brazing is used to join TiAl components, then the components can be connected, but heat-affected zones form that reduce mechanical properties
Solution Approach 1:
The invention replaces thermal field-based joining (welding/brazing) with mechanical field-based cold spraying. This substitution eliminates heat-affected zones entirely, as the cold spray process operates below the recrystallization temperature of TiAl. The high-velocity particle impact and plastic deformation mechanism achieves reliable joining while preserving microstructure integrity and mechanical properties.
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 process enhances the mechanical properties of TiAl components by maintaining a refined microstructure, increasing strength and fatigue life, and reducing processing costs compared to traditional methods.
Implementation Method 1
cold spraying titanium aluminide onto an article within a treatment region to form a titanium aluminide surface
Data Source
AI summary
A titanium aluminide application process and article with a titanium aluminide surface are disclosed. The process includes cold spraying titanium aluminide onto an article within a treatment region to form a titanium aluminide surface. The titanium aluminide surface includes a refined gamma/alpha2 structure and/or the titanium aluminide is cold sprayed from a solid feedstock of a pre-alloyed powder.