Halogen-Coated Turbine Wheel Oxidation Resistance
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Solution Overview
Problem
Turbine rotors in exhaust gas turbochargers face challenges with oxidation at high temperatures, which affects the performance and longevity of nickel-based alloys used in turbine wheels and blades, leading to reduced engine response due to increased mass moment of inertia.
Innovation Solution
A method involving a halogen-based protective coating applied to the turbine wheel, followed by heat treatment, and subsequent connection of the shaft to the hub, with strategic removal and reformation of the coating to prevent oxidation and ensure a durable connection, using materials like titanium-aluminum alloys for reduced mass and steel for the shaft.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a low-density material (such as titanium-aluminum alloy) is used for the turbine wheel to reduce mass and improve engine response, then the mass moment of inertia is reduced and engine response is improved, but the material becomes susceptible to oxidation at high temperatures exceeding 800°C
Solution Approach 1:
The patent applies a halogen-based protective coating (such as fluorine, chlorine, bromine, or iodine) to the surface of the turbine wheel made of low-density material. This creates a composite structure where the titanium-aluminum alloy provides low density and the halogen coating provides oxidation resistance at high temperatures, thus resolving the contradiction between reduced mass and maintained reliability.
Solution Approach 2:
The halogen coating acts as an intermediary layer between the low-density turbine wheel material and the oxidizing environment. This intermediary protective layer prevents direct contact between the reactive titanium-aluminum alloy and oxygen, allowing the use of low-density materials without suffering from oxidation issues.
2Reliability
If a protective coating is applied to the entire turbine wheel surface to prevent oxidation, then oxidation resistance is improved, but the complexity of the manufacturing process increases due to additional coating and heat treatment steps
Solution Approach 1:
The patent applies the halogen-based protective coating and performs heat treatment during the manufacturing process before the turbine wheel is put into service. This preliminary action ensures oxidation protection is built-in from the start, preventing future oxidation damage without requiring additional maintenance or complex operational procedures.
Solution Approach 2:
The patent utilizes heat treatment at specific temperatures to activate the halogen coating and form a stable protective layer on the turbine wheel surface. By controlling thermal parameters during manufacturing, the coating transforms into a durable oxidation barrier, achieving reliable protection through parameter optimization rather than process complexity.
3Manufacturing precision
If the shaft is connected to the turbine wheel hub during manufacture to form a complete turbine rotor, then assembly precision is improved, but the protective coating on the hub cannot be properly applied or the connection process becomes more complex
Solution Approach 1:
The patent divides the manufacturing process into separate stages: first, the turbine wheel hub is manufactured and coated with the halogen-based protective coating; second, the shaft is connected to the pre-coated hub to form the complete turbine rotor. This segmentation allows the protective coating to be applied to the hub surface without interference from the shaft, ensuring both coating quality and assembly precision.
Solution Approach 2:
The protective coating is applied to the turbine wheel hub in advance, before the shaft connection is made. This preliminary coating application ensures that the entire hub surface, including areas that would be difficult to coat after assembly, receives adequate protection. The shaft is then connected to this pre-protected hub, maintaining both manufacturing ease and protection effectiveness.
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 method results in a turbine rotor that is resistant to oxidation at high temperatures, reducing mass and improving engine response by forming a thermally resistant protective coating, thereby enhancing the operational efficiency and durability of the exhaust gas turbocharger.
Implementation Method 1
forming a protective coating by applying or incorporating a halogen on or in the surface of the turbine wheel, preferably the entire surface, and subsequently heat treating the turbine wheel
Implementation Method 2
subsequently heat treating the turbine wheel
Implementation Method 3
subsequently heat treating the turbine wheel
Data Source
AI summary
A method for producing a turbine rotor of an exhaust gas turbocharger, wherein the turbine rotor includes a turbine wheel with a hub and turbine blades that extend from the hub, and a shaft, includes the steps of: providing the turbine wheel and the shaft; forming a protective layer by applying or introducing a halogen on or in the surface of the turbine wheel and subsequently heat-treating the turbine wheel; and connecting the shaft to the hub of the turbine wheel after the protective coating is formed.