Porous Ceramic Core Acid Blocking in Turbine Blade Pickling

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Solution Overview

Problem

In investment casting, porous ceramic cores in fluid communication with acid baths during chemical pickling of turbine blades retain acid, leading to material loss, especially in inner surfaces and walls, which can affect the longevity and compliance of the blades.

Innovation Solution

Filling the pores of the ceramic cores with a liquid before chemical pickling to prevent acid penetration, using immersion or injection methods, ensuring the liquid reaches at least 90% to 100% saturation, typically with an aqueous solution like water, to prevent material loss.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If porous ceramic cores are used during investment casting to form complex cavities, then the manufacturing capability for complex geometries is improved, but the ceramic cores retain acid during chemical pickling causing material loss and reducing blade longevity

Engineering Contradiction:

Improvemanufacturing capability for complex geometriesVSAvoidblade longevity

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent applies preliminary action by filling the porous ceramic cores with a liquid (such as water or oil) before the chemical pickling process. This pre-filling prevents the pickling acid from penetrating into the ceramic pores, thereby eliminating material loss while maintaining the cores' structural function for complex cavity formation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses an intermediary substance (liquid filler) that mediates between the ceramic cores and the pickling acid. This intermediary occupies the porous spaces and prevents direct contact between the acid and the core structure, eliminating the harmful acid retention effect while allowing the cores to continue serving their molding function.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Manufacturing precision

If chemical pickling is performed to suppress residual surface stresses, then the surface quality and stress relief are improved, but the porous ceramic cores absorb pickling acid causing material loss in inner surfaces

Engineering Contradiction:

Improvesurface quality and stress reliefVSAvoidmaterial loss in inner surfaces

Core Design Contradiction:

Manufacturing precisionVSLoss of substance

Solution Approach 1:

The patent performs the action of filling ceramic pores with liquid before chemical pickling. This preliminary step prevents acid penetration into the pores, allowing the pickling process to proceed effectively for surface quality improvement without the harmful side effect of material loss from acid absorption.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent converts the potentially harmful acid absorption by ceramic pores into a beneficial protective measure. By intentionally filling pores with a harmless liquid first, the harmful acid is prevented from entering, and the liquid filler acts as a protective barrier that can be easily removed afterward, thus protecting the inner surfaces from material loss.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Loss of substance

If ceramic cores are removed after casting but before pickling, then material loss is avoided, but the process complexity and time increase due to sequential operations

Engineering Contradiction:

Improvematerial loss preventionVSAvoidprocess complexity

Core Design Contradiction:

Loss of substanceVSDevice complexity

Solution Approach 1:

The patent performs the preliminary action of filling ceramic pores with liquid while the cores are still in place during the pickling process. This eliminates the need to remove cores before pickling, as the liquid-filled cores are already protected from acid absorption. The cores can remain in position throughout pickling, simplifying the process sequence.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent merges the core retention function with the acid protection function by filling the pores with liquid. This allows the cores to remain in the mold during pickling without causing material loss, thereby combining the benefits of core retention (maintaining cavity structure) with acid protection (preventing material loss) in a single integrated approach.

Inventive Principle:

Principle #5Merging (Combining)

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

Prevents material loss by blocking acid penetration into the ceramic cores, ensuring accurate dimensions and extended blade longevity by maintaining material integrity during the pickling process.

Implementation Method 1

filling the pores of the ceramic core with a liquid

Methodology Applied

Scientific EffectCapillary action: Capillary Action

Data Source

PatentUS12173415B2Method for chemically pickling a cast metal part with porous ceramic core(s)

Publication Date: 2024.12.24 SAFRAN AIRCRAFT ENGINES SAS

AI summary

A method for chemically pickling a cast metal part, including a metal envelope which delimits an inner space in which at least one porous ceramic core is housed, and an outer space, the ceramic core being in fluid communication with the outer space, which method including: filling the pores of the ceramic core with a liquid; and then chemically pickling the cast metal part. This chemical pickling method may be implemented in a method for manufacturing a metal part by investment casting. This method is applicable at least to manufacture of turbine blades for turbomachines and, especially, for aircraft turbojet engines.