Functionally Graded Impeller for Corrosive Gas
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Solution Overview
Problem
Centrifugal compressors operating with corrosive gases face challenges due to the high cost of traditional corrosion-resistant alloys used for impellers, and existing coating methods are ineffective on complex geometries, leading to partial or no coverage and deformation.
Innovation Solution
A method involving functionally graded materials, where a base metal like carbon steel is used with a corrosion-resistant alloy applied via hot isostatic pressing to form an impeller with a porosity of less than one percent, reducing the amount of expensive alloys needed while maintaining desired material properties, and an external layer is bonded to the intermediate layer to enhance corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional corrosion-resistant alloys are used for impellers in corrosive gas environments, then corrosion protection is improved, but material cost increases significantly
Solution Approach 1:
The patent applies functionally graded materials that transition from base metal in the core to corrosion-resistant alloy at the external surface. This local quality approach places corrosion-resistant material only where it is needed (at the surface exposed to corrosive gases), rather than using expensive alloys throughout the entire impeller structure, thus reducing overall material cost while maintaining corrosion protection.
Solution Approach 2:
The patent utilizes composite material structures combining base metal and corrosion-resistant alloys in a functionally graded configuration. The composite structure integrates materials with different properties in a controlled gradient, allowing the impeller to exhibit both the mechanical strength of base metal and the corrosion resistance of specialty alloys, optimizing performance while reducing cost.
2Reliability
If coating methods are used to improve corrosion resistance on impellers, then corrosion protection is enhanced, but manufacturing complexity increases due to geometry constraints
Solution Approach 1:
The patent changes the manufacturing parameter from surface coating application to bulk material composition gradient. By controlling the compositional parameter throughout the material volume during manufacturing, the patent achieves uniform corrosion protection without the geometric limitations and complexity associated with applying coatings to complex impeller surfaces.
3Duration of action of stationary object
If cladding layers are attached to counteract stress corrosion cracking, then durability is improved, but impeller deformation occurs during the attachment process
Solution Approach 1:
The patent merges the base metal and corrosion-resistant alloy into a single functionally graded material structure through controlled diffusion and bonding processes. This merging eliminates the need for separate cladding attachment steps that cause deformation, as the gradient structure is created integrally during manufacturing rather than through subsequent assembly operations.
Solution Approach 2:
The patent performs the material gradient formation and bonding in advance during the manufacturing process, before the impeller undergoes final machining or assembly. This preliminary action ensures that the functionally graded structure is established while the material is still in a formable state, preventing deformation that would occur with post-manufacturing cladding attachment.
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 approach reduces material costs while maintaining acceptable properties for corrosive environments, ensuring effective corrosion protection and thermal expansion compatibility, thus enhancing the durability and efficiency of impellers in centrifugal compressors.
Implementation Method 1
processing with hot isostatic pressing the base metal, the first metal powder and the first insert such that the intermediate layer is bonded to the base metal
Implementation Method 2
The HIP process causes the metal powder to bond to the insert and/or base metal and/or intermediate layer
Data Source
AI summary
Devices and methods provide for an impeller (200) for use in a compressor. A method for manufacturing the impeller includes: attaching an intermediate layer to a base metal by placing a first metal powder into a gap between a first insert and the base metal; processing with hot isostatic pressing the base metal, the first metal powder and the first insert such that the intermediate layer is bonded to the base metal; attaching an external layer to the intermediate layer by placing a second powder into a gap between a second insert and the intermediate layer; processing the base metal, the intermediate layer, the second metal powder and the second insert via hot isostatic pressing such that the external layer is bonded to the intermediate layer; and removing the second insert to form the impeller, wherein the external layer is corrosion resistant.