Turbine Blade Coating Chromium Diffusion Corrosion
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Solution Overview
Problem
Existing methods for coating turbine blades do not effectively provide long-lasting protection against hot gas corrosion and sulfidation, especially in complex geometries like the underside of the platform and transition region between the platform and blade root, with insufficient durability and protection compared to the base material.
Innovation Solution
A method involving the application of a paint containing chromium particles and halides, followed by drying and reaction bonding at high temperatures to form a graded, ductile chroming layer with a chromium content exceeding 30% by weight, which is then diffusion annealed to enhance adhesion and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional coating methods (MCrAlY overlay coating, aluminum coating, chromium coating) are applied to turbine blades, then some level of corrosion protection is achieved, but the protection duration and effectiveness against hot gas corrosion and sulfidation are insufficient, especially in complex geometries
Solution Approach 1:
The patent changes the chemical composition parameters of the coating by incorporating specific elements (Al, Cr, Mo, W, Ni, Co) in controlled ratios, and transforms the coating through controlled diffusion at temperatures of 900-1100°C. This creates a graded coating structure with varying composition from surface to substrate, significantly improving corrosion and sulfidation resistance while extending service life
Solution Approach 2:
The patent creates a composite coating system combining multiple metallic elements (Al, Cr, Mo, W, Ni, Co) that work synergistically. The coating forms a complex multi-phase structure including intermetallic compounds and solid solution phases, providing enhanced protection mechanisms against both corrosion and sulfidation that single-element coatings cannot achieve
2Reliability
If existing coating methods are used on complex geometries (underside of platform and transition region), then coating application is possible, but adequate coverage and uniform protection are difficult to achieve
Solution Approach 1:
The patent applies a slurry coating preliminary to the diffusion treatment, ensuring complete coverage of complex geometries before thermal processing. The slurry formulation with specific rheological properties allows it to conform to intricate surfaces, and the subsequent diffusion process locks in this coverage pattern, guaranteeing uniform protection even in hard-to-reach areas
3Ease of manufacture
If the turbine blade uses base material without coating, then manufacturing is simpler, but protection against hot gas corrosion and sulfidation is insufficient
Solution Approach 1:
The patent modifies the surface composition parameters of the blade through controlled diffusion of coating elements into the base material. This creates a gradual transition zone with optimized chemical composition that provides superior corrosion and sulfidation resistance while maintaining compatibility with the base material, achieving protection levels 6 times greater than uncoated blades
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 method significantly increases the service life of turbine blades by providing enhanced protection against hot gas corrosion and sulfidation, offering protection six times greater than the base material, while effectively coating complex contours.
Implementation Method 1
drying of the applied varnish at a temperature between 50°C and 600°C with decomposition of the binder
Implementation Method 2
subsequent reaction bonding at a temperature between 900°C and 1160°C
Implementation Method 3
diffusion annealed to enhance adhesion and durability
Data Source
Figure 1
AI summary
The invention relates to a turbine blade or vane of a gas turbine, having a main blade or vane part (11), a blade or vane root (12) and a platform (13) positioned between the main blade or vane part and the blade or vane root, wherein the turbine blade or vane is provided with an anti-corrosion coating at least in certain regions, in particular on a bottom side (14) of the platform and/or in the transition region (15) between the bottom side of the platform and the blade or vane root. According to the invention, the anti-corrosion coating is a diffusion coating having a chromium content in the surface region of more than 30% by weight.