Electropolishing HIP Superalloy Components to Remove Diffusion Bands

Solution Overview

Problem

Conventional machining methods are economically and technically prohibitive for removing the diffusion band from hot isostatically pressed components made from advanced nickel base superalloys like RR1000, which can lead to catastrophic part failure due to undesirable material properties.

Innovation Solution

A method involving electropolishing to remove a uniform surface layer from hot isostatically pressed workpieces, maintaining the shape and improving material properties by eliminating diffusion bands, which is more economically viable than conventional machining.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional machining is used to remove the diffusion band, then the material properties are improved, but the manufacturing cost and time increase significantly

Engineering Contradiction:

Improvematerial propertiesVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent replaces conventional mechanical machining with an electrochemical process (electropolishing) to remove the diffusion band. This substitution eliminates the difficulties associated with machining RR1000 superalloy while achieving the same goal of removing the contaminated surface layer, thereby reducing manufacturing cost and time.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the approach from mechanical removal to electrochemical removal by applying electrical parameters (current density, electrolyte composition, temperature) to control the material removal process. This parameter change enables efficient removal of the diffusion band without the high costs and time consumption of conventional machining.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If conventional machining is used to remove the diffusion band, then the material properties are improved, but the production time increases

Engineering Contradiction:

Improvematerial propertiesVSAvoidproduction time

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent replaces conventional mechanical machining with an electrochemical process (electropolishing) to remove the diffusion band. This substitution eliminates the difficulties associated with machining RR1000 superalloy while achieving the same goal of removing the contaminated surface layer, thereby reducing manufacturing cost and time.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The electropolishing process allows for continuous material removal without the intermittent stopping and starting required in conventional machining. The process can be maintained at optimal parameters throughout, enabling faster and more efficient removal of the diffusion band.

Inventive Principle:

Principle #20Continuity of useful action

3Reliability

If the whole outer surface is machined to remove the diffusion band, then the material properties are improved, but the part cost becomes unacceptably high

Engineering Contradiction:

Improvematerial propertiesVSAvoidpart cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent replaces conventional mechanical machining with an electrochemical process (electropolishing) to remove the diffusion band. This substitution eliminates the difficulties associated with machining RR1000 superalloy while achieving the same goal of removing the contaminated surface layer, thereby reducing manufacturing cost and time.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the approach from mechanical removal to electrochemical removal by applying electrical parameters (current density, electrolyte composition, temperature) to control the material removal process. This parameter change enables efficient removal of the diffusion band without the high costs and time consumption of conventional machining.

Inventive Principle:

Principle #35Parameter changes

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 effectively removes the diffusion band, enhancing the creep-life performance of components while maintaining the shape, thus reducing the risk of part failure and lowering production costs.

Implementation Method 1

electropolishing a surface of the workpiece to remove a substantially uniform surface layer of the workpiece

Methodology Applied

Scientific EffectElectropolishing: Electrolysis

Implementation Method 2

The temperatures and pressures applied during the HIP process are sufficiently high within the HIP vessel to diffusion bond the RR1000 powder particles together into a workpiece

Methodology Applied

Scientific EffectDiffusion bonding: Diffusion

Implementation Method 3

Hot Isostatic Pressing (HIP) is a near net shape technique which can be used to form RR1000 combustor casings

Methodology Applied

Scientific EffectHot isostatic pressing: Hot Isostatic Pressing

Data Source

PatentUS9023188B2Component production method

Publication Date: 2015.05.05 ROLLS ROYCE PLC

AI summary

A method of producing a component includes the steps of: providing a workpiece generated by hot isostatic pressing a powder metal form; and electropolishing a surface of the workpiece to remove a substantially uniform surface layer of the workpiece to produce the component. Following the electropolishing step, the component has substantially the same shape as the workpiece produced by the hot isostatic pressing step.