Mo-Si-B Alloy Powder Formation via Segmented Thermal Treatment
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Solution Overview
Problem
Molybdenum (Mo) and Mo-based alloys face limitations in elevated temperature applications due to poor oxidation resistance, with molybdenum trioxide sublimation leading to accelerated metal loss in oxidizing environments, necessitating externally applied coatings for use in non-oxidizing conditions, and requiring specific processing for desired microstructure and phase assembly in Mo-Si-B alloys.
Innovation Solution
A method involving the formation of Mo-Si-B alloy powder through a mixture of Mo, Si3N4, and BN powders with a polymer binder, followed by spray drying, thermal treatment to remove the binder and alloy the powders, and subsequent milling in a Mo-based material environment to reclaim fine powder, minimizing contamination and oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Mo-Si-B alloys are thermally treated to achieve desired microstructure and phase assembly, then mechanical properties and oxidation resistance are improved, but partial sintering occurs forming pieces that are more difficult to process
Solution Approach 1:
The thermal treatment process is segmented into controlled stages with specific temperature ranges and time periods. The first stage removes binder and volatile contaminants, while the second stage achieves alloying and desired microstructure. This segmentation prevents excessive sintering that would make processing difficult, while still achieving the necessary oxidation resistance and mechanical properties.
Solution Approach 2:
The powder mixture is prepared with specific composition ratios of Mo, Si3N4, and BN powders before thermal treatment. The polymer binder is added in controlled amounts to facilitate green strength during handling but is designed to be completely removed in the first thermal treatment stage. This preliminary preparation ensures that the subsequent thermal treatment achieves the desired microstructure without excessive sintering.
2Reliability
If thermal treatment is applied to alloy the powders and remove contaminants, then oxidation resistance is improved, but binder removal and alloying require controlled atmosphere and time
Solution Approach 1:
The thermal treatment process utilizes controlled changes in temperature, atmosphere composition, and time parameters. The first stage operates at lower temperature (e.g., 500-800°C) in inert or reducing atmosphere to remove binder and volatile contaminants. The second stage operates at higher temperature (e.g., 900-1100°C) to achieve alloying and desired microstructure. These parameter changes enable effective contaminant removal and alloying while controlling the degree of sintering.
3Ease of manufacture
If fine powder is produced directly, then ease of processing is improved, but oxidation and contamination occur more readily during handling
Solution Approach 1:
The polymer binder and thermal treatment process are designed to maintain the powder in a protected environment. The binder protects fine powder particles during handling and green成型. During thermal treatment, the first stage operates in inert or reducing atmosphere to prevent oxidation while removing the binder. This approach allows fine powder to be processed without excessive oxidation or contamination, while still achieving the desired fine final powder morphology.
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
This process enables the production of high-temperature structural materials with improved mechanical properties and oxidation resistance, suitable for applications like gas turbine engines, by maintaining the integrity and purity of the Mo-Si-B alloy powder, reducing contamination, and preventing oxidation.
Implementation Method 1
spray drying the slurry to form a spray dried powder containing Mo powder, Si3N4 powder and BN powder particles
Implementation Method 2
thermally treating the spray dried powder to remove the binder, alloy the powders of the spray dried powder, and remove carbon, nitrogen and oxygen atoms
Implementation Method 3
alloy the powders of the spray dried powder
Implementation Method 4
remove carbon, nitrogen and oxygen atoms
Implementation Method 5
milling the partially sintered Mo-Si-B alloy powder pieces to break down the pieces
Data Source
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AI summary
A method of forming Mo-Si-B alloy powder includes preparing a mixture that includes Mo powder, Si3N4 powder and BN powder, adding a polymer binder and liquid to the mixture to form a slurry, spray drying the slurry to form a spray dried powder containing Mo powder, Si3N4 powder and BN powder particles, and thermally treating the spray dried powder to remove the binder, alloy the powders of the spray dried powder, and remove carbon, nitrogen and oxygen atoms, wherein thermally treating the spray dried powder forms at least some partially sintered Mo-Si-B alloy powder pieces. The partially sintered Mo-Si-B alloy powder pieces are then milled in a milling container having contact surfaces composed of Mo-based material or lined and/or coated with Mo-based material to break down the pieces, and the milled Mo-Si-B alloy powder pieces are sieved to reclaim the Mo-Si-B alloy powder.