Abradable Coating for Conveyor Rolls in High-Temperature Aluminum Applications
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Solution Overview
Problem
Conveyor rolls made of materials like fused silica suffer from aluminum corrosion and build-up issues when used in high-temperature applications, leading to reduced lifespan due to reactions with molten aluminum and oxidation products.
Innovation Solution
An abradable coating comprising 83-98 wt% of Si3N4, SiC, or SiAlON particles with 2-17 wt% submicronic particles is applied, which is partially removed by wear and friction, maintaining corrosion resistance and allowing for self-regeneration of the coating surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a hard silicon nitride coating is used to prevent aluminum corrosion, then corrosion resistance is improved, but build-up phenomena persist on the surface
Solution Approach 1:
The coating hardness parameter is changed from hard to soft/abradable. The patent applies a soft coating that is intentionally designed to be abradable, allowing it to wear away and remove build-up substances while maintaining corrosion resistance through the underlying hard substrate.
Solution Approach 2:
A soft intermediate coating layer is introduced between the hard substrate and the build-up substances. This intermediate soft coating acts as a mediator that can be easily removed to take build-up with it, while the hard substrate provides the corrosion resistance.
2Ease of repair
If a soft coating is used to remove build-up by wear, then ease of maintenance is improved, but corrosion resistance deteriorates
Solution Approach 1:
The coating system is segmented into two distinct layers: a hard substrate layer providing corrosion resistance and a soft coating layer providing ease of maintenance. Each layer performs its specific function independently, resolving the contradiction between durability and maintainability.
Solution Approach 2:
The invention uses a composite structure combining hard and soft materials. The hard substrate (silicon nitride or similar) provides corrosion resistance, while the soft coating layer (organic polymer-based) provides ease of removal and maintenance, creating a composite system that achieves both benefits.
3Stability of the object's composition
If an organic solvent is used in the coating to avoid hydrolysis, then coating stability is improved, but manufacturing complexity increases
Solution Approach 1:
The solvent type parameter is changed from water-based to organic solvent-based. This parameter change prevents hydrolysis of the silicon nitride particles during coating application, maintaining coating stability while the organic solvent evaporates cleanly without leaving residues.
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 prevents aluminum corrosion, extends the roll's lifespan by removing build-up substances, and can be easily regenerated, ensuring prolonged service life and ease of maintenance.
Implementation Method 1
The coating is abradable and is partially removed by wear together with the build-up substances leaving a clean surface
Implementation Method 2
The coating is abradable and is partially removed by wear together with the build-up substances
Implementation Method 3
Si3N4 is slowly oxidized at the surface resulting in the formation of silica
Data Source
Figure 1(a)~1
AI summary
The present application relates to a protective and abradable coating composition for application on rolls and more particularly to conveyor rolls comprising an abradable coating for use in high temperature applications, to a process for making such rolls and to the use thereof. Corrosion by aluminium melt is reduced and build-up substances are removed by friction. The life time of the roll is then increased. The coating comprises 83-98 wt% of an aggregate comprising particles of Si3N4, SiC or SiAION or a mixture thereof and 2-17 wt% of submicronic particles of AI2O3, SiO2, ZrO2, CeO2, Y2O3 or a mixture thereof.