TiAl Rotor Wheel Fusion Welding Barrier Layer
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Solution Overview
Problem
Current methods for attaching titanium-aluminum (TiAl) turbine wheels to steel shafts in exhaust-gas turbochargers are time-consuming, costly, and prone to forming brittle phases due to the limitations of fusion welding methods, as TiAl base alloys react with nickel-based alloys, preventing effective metallurgical connections.
Innovation Solution
A barrier layer, such as zirconium dioxide, is introduced between the TiAl base alloy and a vanadium-based fusion-weldable attachment layer to prevent atomic diffusion during thermal treatment, allowing for a reliable and cost-effective fusion welding connection by forming a diffusion barrier that prevents the formation of brittle phases and ensures a stable attachment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fusion welding methods are used to join TiAl turbine wheel to steel shaft, then joining speed and reliability are improved, but brittle phases form between Ti, Fe and Al preventing effective welding
Solution Approach 1:
A barrier layer made of refractory metal oxide (such as alumina, silica, magnesia, or titania) is introduced as an intermediary between the TiAl turbine wheel and the steel shaft. This barrier layer prevents direct contact and interdiffusion between TiAl and steel during welding, blocking the formation of brittle phases while allowing the welding process to proceed effectively.
Solution Approach 2:
The barrier layer is applied as a consumable protective coating that serves its purpose during the welding process and can be removed or degraded afterward. This disposable approach allows the use of efficient fusion welding methods without the need for complex permanent barrier structures.
2Ease of manufacture
If intermediate pieces made of Ni base alloys are attached to TiAl turbine wheel by diffusion welding or friction welding, then weldability to steel is improved, but production time and cost increase
Solution Approach 1:
Instead of using thick intermediate pieces requiring diffusion or friction welding, a thin barrier layer of refractory metal oxide is applied to the TiAl surface. This layer acts as a welding barrier that enables direct fusion welding to steel without the need for time-consuming intermediate attachment processes.
Solution Approach 2:
The invention changes the protective approach from thick intermediate layers requiring low-speed diffusion welding to a thin oxide barrier layer enabling high-speed fusion welding. This parameter change in both layer thickness and welding method dramatically reduces production time.
3Ease of manufacture
If intermediate layer made of Ni base alloy is applied by powder spraying methods, then weldability to steel is improved, but production cost increases and metallurgical connection is not achieved
Solution Approach 1:
A barrier layer of refractory metal oxide (such as alumina, silica, magnesia, or titania) is introduced as an intermediary between the TiAl turbine wheel and the steel shaft. This barrier layer prevents direct contact and interdiffusion between TiAl and steel during welding, blocking the formation of brittle phases while allowing the welding process to proceed effectively.
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 solution enables a cost-effective and efficient attachment of TiAl rotor wheels to steel shafts via fusion welding, preventing atomic interdiffusion and ensuring a strong, integral connection without forming brittle phases, thus overcoming the limitations of existing methods.
Implementation Method 1
a barrier layer, which, on account of its properties, is designed to prevent a reaction of the atoms of a first alloy of a main body with the atoms of a second alloy of a fusion-weldable attachment layer during a thermal treatment
Implementation Method 2
during a thermal treatment. In other words, that is to say that the barrier layer according to the disclosure effectively prevents the interdiffusion of the types of atom from the first alloy to the second alloy
Data Source
AI summary
A method for producing a component, in particular a rotor wheel, includes positioning a main body, a fusion-weldable attachment layer, and a barrier layer. The main body has a first alloy in an attachment region. The fusion-weldable attachment layer is positioned in the attachment region of the main body and has a second alloy which differs from the first alloy. The barrier layer is positioned between the main body and the fusion-weldable attachment layer. The barrier layer is configured to prevent a reaction of the first alloy of the main body with the second alloy of the fusion-weldable attachment layer during a thermal treatment. The method further includes heating the main body, the barrier layer, and the fusion-weldable attachment layer to connect the main body, the barrier layer, and the fusion-weldable attachment layer to one another.