Nickel Aluminide Coating Segmentation for Macroparticle Defects

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Solution Overview

Problem

Nickel aluminide coatings deposited via cathodic arc techniques suffer from macroparticle defects, oxidation performance issues, and manufacturing difficulties due to the brittle nature of NiAl materials, necessitating improvements in coating processes and alloying capabilities to reduce costs and shorten coating times.

Innovation Solution

A coating system where nickel and at least one alloy element are sourced separately from aluminum, using a multi-layer cathodic arc deposition process with heat treatment to achieve a uniform distribution of aluminum throughout the coating thickness, reducing the reliance on brittle NiAl cathodes and enhancing manufacturing ease.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If cathodic arc deposition is used to deposit nickel aluminide coatings, then the coating can be applied to metallic substrates, but macroparticle defects occur and oxidation performance is reduced

Engineering Contradiction:

Improvecoating deposition capabilityVSAvoidoxidation performance

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The coating system is segmented into multiple distinct layers: a nickel-containing layer deposited from a nickel-based consumable, and an aluminum layer deposited from a separate aluminum consumable. This segmentation prevents macroparticle defects by avoiding the need to deposit brittle NiAl cathodes while maintaining oxidation resistance through proper layer composition and structure.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention uses a composite coating structure with distinct nickel-containing and aluminum layers that are deposited separately and then reacted to form a nickel aluminide coating. This composite approach allows each layer to be optimized independently, improving oxidation performance while eliminating macroparticle defects associated with homogeneous NiAl cathodes.

Inventive Principle:

Principle #40Composite materials

2Stability of the object's composition

If nickel and aluminum are deposited together from a homogenous NiAl cathode, then uniform chemistry is achieved, but the cathode is difficult to manufacture due to brittleness

Engineering Contradiction:

Improvechemistry uniformityVSAvoidcathode manufacturing

Core Design Contradiction:

Stability of the object's compositionVSEase of manufacture

Solution Approach 1:

Instead of using a single homogenous NiAl cathode, the system segments the cathode materials into separate nickel-based and aluminum consumables. Each consumable can be manufactured independently without the manufacturing difficulties associated with brittle NiAl materials, while the final coating achieves uniform chemistry through controlled reaction during processing.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The nickel-containing layer is deposited first, followed by the aluminum layer, creating a precursor structure that will react to form the final nickel aluminide coating. This preliminary deposition of separate layers avoids the need to manufacture difficult NiAl cathodes while setting up the composition for uniform final coating chemistry.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If a two-step method with pure aluminum deposited over NiAl(CrZr) is used, then macroparticles are covered, but aluminum surface level increases and compositional gradient forms

Engineering Contradiction:

Improvemacroparticle coverageVSAvoidaluminum concentration uniformity

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The system deposits a nickel-containing layer with specific composition and thickness, followed by an aluminum layer with controlled thickness. This local control of layer compositions and the subsequent reaction process achieve macroparticle coverage while minimizing excessive aluminum surface enrichment and compositional gradients through optimized processing parameters.

Inventive Principle:

Principle #3Local quality

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 solution provides a dense, uniformly composed nickel aluminide coating with improved oxidation performance and reduced manufacturing challenges, suitable for use as bond coats or environmental coatings on metallic substrates, such as nickel base superalloys.

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

subsequent processing leads to the formation of a substantially single-phase reacted coating layer comprising nickel aluminide

Methodology Applied

Scientific EffectHeat treatment: Heat Treatment

Data Source

PatentUS8632890B2Nickel aluminide coating systems and coated articles

Publication Date: 2014.01.21 GENERAL ELECTRIC CO

AI summary

A method for forming a nickel aluminide based coating on a metallic substrate includes providing a first 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 to provide the coating precursor on a metallic substrate. The coating precursor may be provided in discrete layers, or from a co-deposition process. Subsequent processing or heat treatment forms the nickel aluminide based coating from the coating precursor.