TiAl Workpiece Induction Preheating for Welding Stress Control
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Solution Overview
Problem
Titanium aluminides are challenging to weld due to their high melting temperature, making temperature control difficult, especially in localized areas like acute-angled contour transitions, which complicates repair and armor coatings.
Innovation Solution
A method involving local inductive preheating of the workpiece to a predetermined temperature, followed by the application of titanium aluminide-based additive layers using build-up welding techniques like laser or plasma welding, with controlled cooling to manage thermal stresses and heat-affected zones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If overlay welding is used to apply material layers to TiAl workpiece, then surface finishing and repair can be achieved, but temperature control becomes difficult and thermal stresses increase due to high melting point of TiAl
Solution Approach 1:
The workpiece is preheated to a predetermined temperature before the cladding welding process. This preliminary heating action reduces the temperature differential during welding, making temperature control easier and reducing thermal stresses in the TiAl workpiece during the overlay welding process.
2Area of stationary object
If localized area heating is applied for repair work, then heat-affected area is reduced, but thermal stresses within the component become difficult to manage
Solution Approach 1:
By preheating the localized area before welding, the thermal gradient is reduced, which prevents excessive thermal stresses from developing during the welding process. This preliminary heating ensures that the heat-affected area remains localized while thermal stresses are kept manageable.
Solution Approach 2:
The predetermined preheating temperature is carefully selected to be below the critical temperature for brittle/ductile phase transition of TiAl. This parameter control ensures that the material remains in a ductile state during localized heating, preventing thermal stress-induced cracking while maintaining a limited heat-affected area.
3Ease of manufacture
If conventional cladding welding is used on TiAl, then material layers can be applied, but additional energy requirements increase due to high melting point
Solution Approach 1:
Preheating the workpiece before cladding welding reduces the energy gap that needs to be bridged during the welding process. By bringing the workpiece closer to the melting temperature beforehand, the additional energy required during actual welding is reduced, making material layer application more energy-efficient.
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 method allows for precise temperature control and reduced thermal stresses, enabling effective surface finishing, armor coating, and repair of titanium aluminide components, particularly in complex geometries like Z-grooves, by limiting the heat-affected area and ensuring the transition areas remain below critical temperatures.
Implementation Method 1
heating the workpiece in a locally limited area by means of induction to a predetermined preheating temperature
Implementation Method 2
applying an additive, preferably in powder form, to the heated surface of the workpiece by means of cladding welding, in particular laser, plasma, micro-plasma, TIG or micro-TIG cladding welding
Implementation Method 3
applying an additive, preferably in powder form, to the heated surface of the workpiece by means of cladding welding, in particular laser, plasma, micro-plasma, TIG or micro-TIG cladding welding
Data Source
Figure 1
AI summary
According to the invention, a process for applying layers of material to a workpiece made of a material which comprises or consists of a titanium aluminide comprises the following steps: the workpiece is prepared; the workpiece is heated to a predefined preheating temperature in a locally delimited region by means of induction; and a, preferably pulverulent, additive is applied to the heated surface of the workpiece by means of build-up welding, in particular laser build-up welding, plasma build-up welding, micro-plasma build-up welding, TIG build-up welding or micro-TIG build-up welding, wherein the additive comprises a titanium aluminide.