Cold Spray Coating for Superalloy Substrates
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Solution Overview
Problem
High-temperature materials used in components like gas turbine assemblies face a trade-off between mechanical properties and resistance to corrosion and oxidation, with coatings like MCrAlX often reducing low-cycle fatigue life due to brittle phases resulting from rapid solidification artifacts in the manufacturing process.
Innovation Solution
A method involving heat-treating metallic powders to remove rapid solidification artifacts and using a deposition technique that does not melt a majority of the particulates, such as cold-spraying, to create a coating with a microstructure free of deleterious phases, enhancing mechanical properties and oxidation resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If combustion thermal spray techniques are used to apply MCrAlX coatings, then oxidation and corrosion resistance is improved, but the coating contains rapid solidification artifacts that reduce mechanical properties and increase brittleness
Solution Approach 1:
The patent applies preliminary heat treatment to the metallic powder before spraying to remove rapid solidification artifacts. This pre-processing step modifies the powder microstructure in advance, eliminating deleterious phases before the coating is applied, thereby preventing mechanical property degradation while maintaining oxidation resistance.
Solution Approach 2:
The patent changes the thermal parameters by using cold spray techniques that do not melt the metallic powder particles. Instead of conventional high-temperature combustion spray that causes rapid solidification, the cold spray process maintains particles in a solid state or partially molten state, fundamentally altering the solidification behavior and eliminating artifact formation.
2Ease of manufacture
If conventional combustion spray processes are used, then coating deposition is achieved, but oxygen content increases making the coating more brittle and less formable
Solution Approach 1:
The patent employs an inert or controlled atmosphere during the cold spray process to prevent oxidation of the metallic powder particles. By maintaining a low-oxygen environment during deposition, the coating achieves lower oxygen content, improved formability, and reduced brittleness while still achieving complete coverage.
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 results in coated articles with improved mechanical performance and reduced crack initiation sites, maintaining the desired microstructure of the substrate while providing enhanced resistance to high-temperature corrosion and oxidation.
Implementation Method 1
heat-treating a quantity of metallic powder, the powder having particulates comprising at least two elements and a plurality of rapid solidification artifacts present within the particulates
Implementation Method 2
the heat-treating is performed at a combination of time and temperature effective to remove substantially all of the rapid solidification artifacts from the powder
Implementation Method 3
combustion cold spray techniques such as those disclosed in commonly assigned U.S. Patent Application Number 12/790,170 have been developed to enable formation of dense deposits of materials without substantially heating the materials above their melting points
Implementation Method 4
gas pressures to impart velocity to the particles
Implementation Method 5
a substrate made of a nickel-based superalloy may be coated with an oxidation-resistant material such as a so-called 'MCrAlX' coating, that is, a coating that includes chromium, aluminum
Implementation Method 6
enhance component surface properties... to enhance certain properties of the material
Data Source
Figure 1
AI summary
An article 100 includes a substrate 110 comprising a precipitate-strengthened alloy and a coating 120 disposed over the substrate 110. The alloy comprises a) a population of gamma-prime precipitates, the population having a multimodal size distribution with at least one mode corresponding to a size of less than about 100 nanometers; or b) a population of gamma-double-prime precipitates having a median size less than about 300 nanometers. The coating 120 comprises at least two elements, and further comprises a plurality of prior particles. At least a portion of the coating 120 is substantially free of rapid solidification artifacts. Methods for fabricating the article 100 and for processing powder useful for fabricating the article 100 are also provided.