Diffusion Barrier Coating for Nickel-CBN Blade Tip
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Solution Overview
Problem
In gas turbine engines, the nickel integrally bladed rotor tip Ni-CBN coating experiences premature degradation due to diffusion of elements like Cr and Al from the base super alloy, leading to oxide formation and strength reduction.
Innovation Solution
A diffusion barrier coating comprising a nickel cobalt and chromium-aluminum-yttria powder material is applied between the nickel-based alloy substrate and the nickel-cubic boron nitride composite material, preventing element diffusion and oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a Ni-CBN coating is applied to the nickel-based alloy substrate, then the wear resistance and surface properties are improved, but element diffusion occurs leading to coating degradation and loss of mechanical strength
Solution Approach 1:
A diffusion barrier layer comprising nickel, cobalt, chromium, aluminum, and yttria is introduced as an intermediary between the nickel-based alloy substrate and the Ni-CBN composite coating. This barrier layer prevents direct contact and element diffusion between the substrate and coating, thereby maintaining coating strength and stability during engine operation and heat treatment.
2Temperature
If heat treatment or engine operation is performed, then the desired thermal and mechanical properties are achieved, but element diffusion into the coating occurs causing oxide formation and strength reduction
Solution Approach 1:
The diffusion barrier layer acts as a protective intermediary that prevents element diffusion during heat treatment and engine operation. By blocking the diffusion path of Cr, Al, and other elements, the barrier layer prevents oxide formation at the substrate-coating interface even when exposed to high temperatures, thereby eliminating the harmful effect of oxidation.
3Quantity of substance
If Cr and Al elements diffuse from the substrate into the coating, then the coating gains initial compositional benefits, but subsequent oxidation of these elements causes coating recession and loss of CBN particles
Solution Approach 1:
The diffusion barrier layer comprising nickel, cobalt, chromium, aluminum, and yttria serves as a mediator that controls element distribution. It allows the coating to maintain its desired Ni-CBN composition while preventing excessive diffusion of Cr and Al from the substrate. This controlled composition prevents oxidation-induced coating recession and CBN particle loss, thereby extending coating lifetime during engine operation.
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 diffusion barrier effectively prevents Cr, Al, and Ti depletion, reducing grain boundary oxidation, maintaining mechanical strength, and extending the lifetime of the rotor tip by forming a thin, uniform oxidation layer and inhibiting nickel alloy depletion.
Implementation Method 1
A diffusion barrier coating on a nickel-based alloy substrate comprising the diffusion barrier coupled to the substrate between the substrate and a composite material opposite the substrate
Implementation Method 2
As a result of the diffusion of the elements from the base super alloy and the propensity of these elements to oxidize during engine operation, oxides form along surfaces and grain boundaries within the coating
Data Source
Figure 1
Figure 2
AI summary
A diffusion barrier coating on a nickel-based alloy substrate (54) comprising a diffusion barrier (58) being coupled to the substrate (54) between the substrate (54) and a composite material (56) opposite the substrate (54), wherein the diffusion barrier (58) comprises a nickel cobalt and chromium-aluminum-yttria powder material (66).