Lanthanum Molybdate Abradable Coatings for Gas Turbine Blade Tip Protection
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Solution Overview
Problem
In gas turbine engines, ceramic matrix composite (CMC) blade tips are susceptible to wear due to rub events with metal shrouds, leading to increased clearance and reduced engine efficiency, as environmental barrier coatings (EBC) wear away, exposing the CMC blades to high-temperature steam.
Innovation Solution
A lanthanum molybdate-based abradable coating is applied to metal shrouds, which is softer than the EBC and designed to be removed during rub events, preventing wear on the CMC blade tips and maintaining efficient tip clearance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If CMC blade tips are used to reduce weight and increase temperature capability, then engine efficiency and performance are improved, but the blade tips become susceptible to wear from rub events with metal shrouds
Solution Approach 1:
The patent introduces an abradable coating as an intermediary layer between the CMC blade tip and the metal shroud. This coating is specifically designed to be softer than the EBC on the blade tip, so that during rub events, the coating is removed instead of the EBC, thereby protecting the blade tip from wear while maintaining the benefits of CMC materials
Solution Approach 2:
The abradable coating is designed as a sacrificial, consumable layer that is intentionally made to wear away during rub events. By using a softer, more easily removed coating material, the system trades the loss of a replaceable coating for the protection of the expensive, performance-critical CMC blade tip and EBC
2Loss of energy
If tip clearance is reduced to improve engine efficiency, then energy loss is reduced, but the blade tips are brought into closer contact with shrouds increasing rub events and wear
Solution Approach 1:
The abradable coating serves as a protective intermediary that enables the blade tip to operate in close proximity to the shroud without suffering direct wear damage. The coating absorbs the mechanical contact and wear, allowing the system to maintain reduced tip clearance for efficiency while protecting against the harmful effects of rub events
Solution Approach 2:
The patent converts the potentially harmful rub events into a beneficial protective mechanism. By designing the coating to be softer than the EBC, the wear that occurs during rub events selectively removes the coating while preserving the EBC and blade tip, thus transforming mechanical contact from a harmful wear source into a self-protecting mechanism
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 abradable coating effectively reduces wear on CMC blade tips during rub events, maintaining engine efficiency by ensuring consistent tip clearance and preventing exposure to high-temperature steam, thus enhancing turbine performance.
Implementation Method 1
an abradable coating on the surface of the substrate. The abradable coating can comprise La2-xAxMo2-y-y′WyBy′O9-δ forming a crystalline structure
Data Source
AI summary
A coated substrate is provided that can include a substrate defining a surface, and an abradable coating on the surface of the substrate. The abradable coating can comprise La2-xAxMo2-y-y′WyBy′O9-δ forming a crystalline structure, where A comprises Li, Na, K, Rb, Cs, Sc, Y, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Th, Be, Mg, Ca, Sr, Ba, Cu, Bi, Cd, Zn, Ag, Au, Pt, Ir, Rh, Ru, Pd, or combinations thereof; 0<x≤about 0.2 (e.g., about 0.1≤x≤about 0.15); 0≤y≤about 1.5 (e.g., about 0.01≤y≤about 1.5); B comprises Ta, Nb, V, Fe, Cr, Mn, Co, Ni, Sn, Ga, Al, Re, In, S, or combinations thereof; 0≤y′≤about 0.2, wherein the sum of y and y′ is about 0.01 to about 1.6; and 0≤δ≤about 0.2.