Nickel Aluminide Coating via Segmented Cathodic Arc Deposition

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Solution Overview

Problem

Existing nickel aluminide-based coatings on metallic substrates face issues such as macroparticle defects, high manufacturing difficulties due to the brittleness of NiAl materials, and the need for cost reduction and shorter coating times, along with limitations in alloying capabilities.

Innovation Solution

A method involving the separation of aluminum from the coating composition into two distinct consumable sources for cathodic arc deposition, using a multi-layered coating precursor with nickel alloy (NiX) and aluminum layers, followed by heat treatment to achieve a uniform nickel aluminide coating with reduced aluminum surface concentration and improved interdiffusion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If cathodic arc deposition with homogenous NiAl source is used, then uniform chemistry through coating thickness is achieved, but macroparticle defects and shadowing occur

Engineering Contradiction:

Improvechemistry uniformityVSAvoidcoating defect-free quality

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The consumable source is segmented into two separate cathodes: one containing nickel and alloying elements (NiX), and another containing aluminum. This segmentation allows independent control of aluminum content and eliminates macroparticle transfer from homogenous NiAl cathodes, resolving the contradiction between chemistry uniformity and defect-free quality.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Aluminum is extracted from the NiAl consumable and provided separately through a dedicated aluminum cathode. This extraction eliminates the source of macroparticle defects while maintaining the ability to achieve uniform aluminum distribution through controlled deposition and subsequent heat treatment.

Inventive Principle:

Principle #2Taking out (Extraction)

2Manufacturing precision

If pure NiAl consumable is used, then coating composition is achieved, but manufacturing difficulty increases due to brittleness

Engineering Contradiction:

Improvecoating compositionVSAvoidcathode manufacturability

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The NiAl consumable is segmented into two separate cathodes with distinct compositions: NiX cathode (nickel plus alloying elements) and Al cathode (aluminum). Each cathode uses a ductile material suitable for its specific composition, eliminating the brittleness and manufacturing difficulties associated with pure NiAl consumables.

Inventive Principle:

Principle #1Segmentation

3Reliability

If aluminum layer is deposited over NiAl layer, then macroparticles are covered through interdiffusion, but aluminum surface concentration increases and compositional gradient forms

Engineering Contradiction:

Improvemacroparticle coverageVSAvoidaluminum concentration control

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

Instead of depositing a thick aluminum layer that would create excessive surface aluminum concentration, the invention uses controlled deposition parameters to provide just enough aluminum to cover macroparticles during heat treatment, achieving the minimum necessary action without excessive aluminum accumulation at the surface.

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

Deposition parameters (current, voltage, deposition rate) are optimized to control aluminum diffusion during the coating process, allowing macroparticle coverage while maintaining controlled aluminum concentration distribution and avoiding excessive surface enrichment.

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

This approach eliminates manufacturing difficulties, shortens coating times, and provides a more uniform and effective nickel aluminide coating with improved oxidation performance and alloying capabilities, suitable for use as bond coats or environmental coatings on metallic substrates.

Implementation Method 1

cathodic arc (ion plasma) deposition techniques using sources having a generally homogenous composition

Methodology Applied

Scientific EffectCathodic arc deposition: Cathodic Arc Deposition

Implementation Method 2

exhibits high interdiffusion when heated to 1079 °C (1975 °F), thus covering the macroparticles mentioned above

Methodology Applied

Scientific EffectInterdiffusion: Diffusion

Data Source

PatentEP2516689B1Methods of forming nickel aluminide coatings

Publication Date: 2018.04.18 GENERAL ELECTRIC CO

Figure 1~2
Figure 3

AI summary

A nickel aluminide based coating system for a metallic substrate comprises a coating precursor (22), including at least one layer (24a) of nickel and at least one alloy element overlying the metallic substrate (20) obtained from a first source and at least one aluminum layer (26) overlying the metallic substrate (20) obtained from a second source and, optionally, a ceramic thermal barrier coating overlying a coating formed after suitable processing of the coating precursor. A method for forming a nickel aluminide based coating includes providing a source for providing a significant portion of the aluminum content for a coating precursor and a separate nickel alloy source for providing substantially all the nickel and additional alloying elements for the coating precursor. Cathodic arc (ion plasma) deposition techniques may be utilized. The coating precursor may be provided in discrete layers, or from a co-deposition process.