Countergravity Casting Filtration for Sulfur-Controlled Superalloys

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Solution Overview

Problem

Countergravity casting processes introduce sulfur contamination due to prolonged melting in a holding vessel, pickup from refractories, and exposure to the environment, leading to increased sulfur content in cast components, which is not effectively addressed by conventional methods.

Innovation Solution

Incorporation of sulfur-gettering materials such as MgO, CaO, LaO, and Y2O3 in crucibles, molds, and filters, along with the use of oil-less pumps and low-sulfur gases, to reduce sulfur contamination by gettering sulfur from the molten metal and maintaining a controlled environment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If countergravity casting process is used to fill finer features and conserve metal, then productivity and metal efficiency are improved, but sulfur contamination increases due to prolonged melting and exposure

Engineering Contradiction:

Improvecasting efficiencyVSAvoidsulfur contamination

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

A filter containing sulfur-gettering material (such as MgO, CaO, LaO, or Y2O3) is introduced as an intermediary component in the flowpath between the melting crucible and the casting mold. This filter captures sulfur contaminants from the molten metal during the countergravity casting process, allowing the process to maintain both its productivity advantages and low sulfur content in the final casting.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If desulfurized alloys are used to enhance oxidation life, then reliability is improved, but sulfur contamination is lost with the countergravity process for multicrystalline components

Engineering Contradiction:

Improveoxidation lifeVSAvoidsulfur contamination

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

Sulfur-gettering material is introduced into the molten metal either before or during the countergravity casting process. This preliminary action ensures that sulfur contaminants are captured early in the process, preventing the loss of desulfurization benefits that would otherwise occur during the prolonged melting and casting operations.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The sulfur-gettering filter acts as an intermediary that actively removes sulfur contaminants from the molten metal during the countergravity casting process, thereby maintaining the low sulfur content necessary for enhanced oxidation life and reliability of the final component.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Productivity

If prolonged melting in holding vessel is used to fill multiple parts, then productivity is improved, but sulfur pickup from refractories and environment increases

Engineering Contradiction:

Improveparts per meltVSAvoidsulfur pickup

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The sulfur-gettering filter serves as a mediator that captures sulfur contaminants as the molten metal flows through the system during prolonged melting operations. This allows multiple parts to be filled from a single melt while maintaining control over sulfur pickup from refractories and the environment.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The sulfur-gettering filter provides continuous sulfur removal throughout the prolonged melting and casting process, ensuring that sulfur contamination is controlled even as the metal remains in the holding vessel extended periods to fill multiple parts.

Inventive Principle:

Principle #20Continuity of useful action

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

Effectively reduces sulfur content in cast components to levels below or equal to the source superalloy ingots, enhancing the durability and adherence of protective coatings in gas turbine engine components.

Implementation Method 1

Methodology Applied

Scientific EffectGettering: Gettering

Implementation Method 2

a filter along the flowpath. At least one of: the filter comprises a sulfur-gettering material; and a source of sulfur-gettering particles is upstream of the filter and the filter is effective to filter the sulfur-gettering particles

Methodology Applied

Scientific EffectFiltration: Filter (physical)

Implementation Method 3

Countergravity casting relies on differential pressure or vacuum levels to draw metal from a holding melt vessel up vertically into an inverted casting mold through a sprue nozzle

Methodology Applied

Scientific EffectVacuum: Vacuum

Implementation Method 4

Countergravity casting relies on differential pressure or vacuum levels to draw metal from a holding melt vessel up vertically into an inverted casting mold

Methodology Applied

Scientific EffectPressure Gradient: Pressure Gradient

Data Source

PatentUS20260048433A1Countergravity Casting Apparatus and Desulfurization Methods

Publication Date: 2026.02.19 RTX CORP

AI summary

An apparatus for countergravity casting a metallic material, has: a crucible for holding melted metallic material; a casting chamber for containing a mold; a fill tube capable of extending into the crucible to communicate melted metallic material to the casting chamber; and a gas source coupled to a headspace of the melting vessel to allow the gas source to pressurize the headspace to establish a pressure differential to force the melted metallic material upwardly through said fill tube into the mold. Extraneous sulfur is prevented from entering the molten metal from the mold by solidifying metal in the fill tube.