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Spray coating processing SPRAY PROCESSING
Thermal Spraying Spherical Magnesium Oxide Powder
Coatings prepared from thermally sprayed spherical magnesium oxide exhibit excellent resistance to high-temperature oxidation, as well as to erosion by a variety of molten metals and alkaline slag. They are suitable for repairing alkaline refractory linings in metallurgical furnace equipment, exhaust pipes of internal combustion engines, bodies of oxygen lances used in steelmaking furnaces, protective coatings for thermocouple sheaths, and high-temperature oxidation-resistant coatings for heat exchanger tanks.
Product Description
Thermal Spraying Spherical Magnesium Oxide Powder
Coatings prepared from thermally sprayed spherical magnesium oxide exhibit excellent resistance to high-temperature oxidation, as well as to erosion by a variety of molten metals and alkaline slag. They are suitable for repairing alkaline refractory linings in metallurgical furnace equipment, exhaust pipes of internal combustion engines, bodies of oxygen lances used in steelmaking furnaces, protective coatings for thermocouple sheaths, and high-temperature oxidation-resistant coatings for heat exchanger tanks.
Let’s explore this in detail. Thermal Spraying Spherical Magnesium Oxide MgO ) Powder Performance and applications.
First, we need to clarify a key point: Magnesium oxide is typically not used as a primary coating material for surface protection of mechanical components—this is fundamentally different from materials such as tungsten carbide and chromium oxide. Its application is more focused on Functional coating , rather than Wear- and corrosion-resistant coating 。
This is determined by the physicochemical properties of magnesium oxide itself.
I. Core Performance of Magnesium Oxide Powder (for Thermal Spraying)
1. Extremely high melting point ( 2852°C ) ：
* This is significantly higher than the temperature of a conventional plasma spray flame. This means that the magnesium oxide powder undergoes... It's difficult to melt thoroughly. As a result, the resulting coating is highly porous and exhibits poor bonding strength. This is the primary factor limiting its use as a structural coating.
2. High heat resistance and insulation performance ：
* Magnesium oxide is an excellent high-temperature insulating material with stable chemical properties, and it maintains good insulation performance especially at high temperatures.
3. A larger coefficient of thermal expansion ( ~13.5×10⁻⁶/°C ) ：
* This value is higher than that of most metal matrices (such as steel, ~12×10⁻⁶/°C ) is high, but lower than that of many other ceramics (such as alumina, ~8×10⁻⁶/°C ) Also, it needs to be high. This means that the coating is prone to generating significant internal stresses during cooling and thermal cycling, increasing the risk of cracking and delamination.
4. Resistant to alkali slag erosion but with poor acid resistance. ：
* Magnesium oxide is a basic oxide with excellent resistance to alkaline environments, but it readily reacts with acidic substances.
5. “ Spherical ” Advantages of powder form ：
* High liquidity The spherical powder particles exhibit excellent flowability, enabling stable and uniform powder delivery during the spraying process—a prerequisite for obtaining a consistent coating.
* Uniform density : Helps to form a more uniform coating structure.
II. Applicability of Thermal Spraying Processes
Due to magnesium oxide's extremely high melting point, Only high-temperature spraying processes can be applicable. ：
* Atmospheric Plasma Spraying ( APS ) Yes. The only feasible one A conventional choice. The plasma flame jet is one of the few heat sources capable of approaching or reaching the melting point of magnesium oxide. However, even under these conditions, insufficient melting remains a common issue, necessitating careful optimization of parameters such as high power and low powder feed rate.
* Supersonic Flame Spraying HVOF/HVAF ) ： Not applicable Its flame temperature (approximately 2500-3000°C ) is insufficient to melt magnesium oxide powder.
III. Main Uses and Application Fields (primarily functional)
Based on the above-mentioned performance, thermal-sprayed magnesium oxide coatings have very specific applications, primarily concentrated in fields that require their exceptional high-temperature properties:
1. Heat-resistant and thermal-insulating coating for high-temperature furnaces and kilns
* Application When applied to the inner walls of metal furnace chambers or heating elements, its high melting point and thermal resistance provide a degree of high-temperature resistance and thermal insulation. However, due to issues with coating adhesion strength and thermal shock resistance, this application is not as effective as that of other ceramics—such as yttria-stabilized zirconia. YSZ ) Common.
2. In plasma spraying “ Sacrifice ” Coating or barrier coating
* Application In the spraying process of certain special materials, magnesium oxide can be used as a... Removable transition layer or barrier layer For example:
* When spraying certain reactive metals that would undergo a vigorous reaction with the substrate, first apply a layer of magnesium oxide as an isolation barrier.
* After completion, take advantage of magnesium oxide’s property of being readily soluble in acids (except hydrofluoric acid) to dissolve and remove it using an acid, thereby obtaining a net-shaped part or removing the substrate.
3. Intermediate steps in the preparation of functional materials
* Application In scientific research or specific industrial fields, porous magnesium oxide preforms are prepared by spraying and then further processed into functional devices of desired specifications through other techniques such as melt infiltration. This is not a final coating but rather a step in the manufacturing process.
4. High-temperature electrical insulation coating
* Application In extreme environments that require high-temperature electrical insulation but where organic materials cannot be used, magnesium oxide coatings can serve as an alternative. However, the porosity of these coatings may compromise their insulating performance, typically necessitating subsequent pore-sealing treatments.
IV. More Common Applications: As an Additive for Powder Raw Materials
Magnesium oxide powder (whether spherical or not) in the field of thermal spraying—a More important, more common The role is to serve as Stabilizer additive , rather than the main spraying material.
* In zirconia ( Zirconium dioxide ) Applications in thermal barrier coatings ：
* Zirconia undergoes a phase transformation during heating and cooling, accompanied by significant volume changes that can lead to cracking and delamination of the coating.
* Add a certain proportion of Magnesium oxide ( MgO ) As a stabilizer , which can form with zirconium oxide Magnesium-stabilized zirconia ( MSZ - Magnesia-Stabilized Zirconia ) 。
* MSZ It can maintain a stable cubic phase structure at high temperatures, avoiding damage caused by phase transitions, and thus can be used as a high-performance component for parts such as engine blades. Thermal Barrier Coating ( TBC ) However, the most mainstream and highest-performing one at present is... Yttria-stabilized zirconia ( YSZ ) ， MSZ Its applications are relatively few.
Summary
Feature | Description | The impact on thermal spraying |
Extremely high melting point | 2852°C | Difficult to melt, poor adhesion strength of the coating, and prone to looseness and porosity. |
High insulation performance | Excellent high-temperature electrical insulator | Insulating coatings suitable for special operating conditions. |
Alkali resistance | High resistance to erosion by alkaline slag | Suitable for specific corrosive environments. |
Easily soluble in acid | Soluble in most acids except hydrofluoric acid. | Can be used as “ Sacrificable ” The barrier layer. |
Spherical powder | Good liquidity, stable powder delivery. | It is a prerequisite for effective spraying. |
Conclusion:
Thermal Spraying Spherical Magnesium Oxide Powder Non-mainstream wear- and corrosion-resistant coating materials Its primary value lies in:
1. Special functional applications Such as high-temperature thermal insulation, removable sacrificial layers, and high-temperature insulation.
2. As an important additive As a stabilizer for the preparation of magnesium-stabilized zirconia. MSZ Thermal barrier coating materials.
Therefore, when selecting thermal-spray materials, unless there are very specific functional requirements (such as exceptional alkali resistance and the ability to be removed by acid pickling), other, more established ceramic materials with better and more reliable performance are usually given priority.
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Spraying equipment SPRAY EQUIPMENT
Thermal Spraying Spherical Magnesium Oxide Powder
Coatings prepared from thermally sprayed spherical magnesium oxide exhibit excellent resistance to high-temperature oxidation, as well as to erosion by a variety of molten metals and alkaline slag. They are suitable for repairing alkaline refractory linings in metallurgical furnace equipment, exhaust pipes of internal combustion engines, bodies of oxygen lances used in steelmaking furnaces, protective coatings for thermocouple sheaths, and high-temperature oxidation-resistant coatings for heat exchanger tanks.
Product Description
Thermal Spraying Spherical Magnesium Oxide Powder
Coatings prepared from thermally sprayed spherical magnesium oxide exhibit excellent resistance to high-temperature oxidation, as well as to erosion by a variety of molten metals and alkaline slag. They are suitable for repairing alkaline refractory linings in metallurgical furnace equipment, exhaust pipes of internal combustion engines, bodies of oxygen lances used in steelmaking furnaces, protective coatings for thermocouple sheaths, and high-temperature oxidation-resistant coatings for heat exchanger tanks.
Let’s explore this in detail. Thermal Spraying Spherical Magnesium Oxide MgO ) Powder Performance and applications.
First, we need to clarify a key point: Magnesium oxide is typically not used as a primary coating material for surface protection of mechanical components—this is fundamentally different from materials such as tungsten carbide and chromium oxide. Its application is more focused on Functional coating , rather than Wear- and corrosion-resistant coating 。
This is determined by the physicochemical properties of magnesium oxide itself.
I. Core Performance of Magnesium Oxide Powder (for Thermal Spraying)
1. Extremely high melting point ( 2852°C ) ：
* This is significantly higher than the temperature of a conventional plasma spray flame. This means that the magnesium oxide powder undergoes... It's difficult to melt thoroughly. As a result, the resulting coating is highly porous and exhibits poor bonding strength. This is the primary factor limiting its use as a structural coating.
2. High heat resistance and insulation performance ：
* Magnesium oxide is an excellent high-temperature insulating material with stable chemical properties, and it maintains good insulation performance especially at high temperatures.
3. A larger coefficient of thermal expansion ( ~13.5×10⁻⁶/°C ) ：
* This value is higher than that of most metal matrices (such as steel, ~12×10⁻⁶/°C ) is high, but lower than that of many other ceramics (such as alumina, ~8×10⁻⁶/°C ) Also, it needs to be high. This means that the coating is prone to generating significant internal stresses during cooling and thermal cycling, increasing the risk of cracking and delamination.
4. Resistant to alkali slag erosion but with poor acid resistance. ：
* Magnesium oxide is a basic oxide with excellent resistance to alkaline environments, but it readily reacts with acidic substances.
5. “ Spherical ” Advantages of powder form ：
* High liquidity The spherical powder particles exhibit excellent flowability, enabling stable and uniform powder delivery during the spraying process—a prerequisite for obtaining a consistent coating.
* Uniform density : Helps to form a more uniform coating structure.
II. Applicability of Thermal Spraying Processes
Due to magnesium oxide's extremely high melting point, Only high-temperature spraying processes can be applicable. ：
* Atmospheric Plasma Spraying ( APS ) Yes. The only feasible one A conventional choice. The plasma flame jet is one of the few heat sources capable of approaching or reaching the melting point of magnesium oxide. However, even under these conditions, insufficient melting remains a common issue, necessitating careful optimization of parameters such as high power and low powder feed rate.
* Supersonic Flame Spraying HVOF/HVAF ) ： Not applicable Its flame temperature (approximately 2500-3000°C ) is insufficient to melt magnesium oxide powder.
III. Main Uses and Application Fields (primarily functional)
Based on the above-mentioned performance, thermal-sprayed magnesium oxide coatings have very specific applications, primarily concentrated in fields that require their exceptional high-temperature properties:
1. Heat-resistant and thermal-insulating coating for high-temperature furnaces and kilns
* Application When applied to the inner walls of metal furnace chambers or heating elements, its high melting point and thermal resistance provide a degree of high-temperature resistance and thermal insulation. However, due to issues with coating adhesion strength and thermal shock resistance, this application is not as effective as that of other ceramics—such as yttria-stabilized zirconia. YSZ ) Common.
2. In plasma spraying “ Sacrifice ” Coating or barrier coating
* Application In the spraying process of certain special materials, magnesium oxide can be used as a... Removable transition layer or barrier layer For example:
* When spraying certain reactive metals that would undergo a vigorous reaction with the substrate, first apply a layer of magnesium oxide as an isolation barrier.
* After completion, take advantage of magnesium oxide’s property of being readily soluble in acids (except hydrofluoric acid) to dissolve and remove it using an acid, thereby obtaining a net-shaped part or removing the substrate.
3. Intermediate steps in the preparation of functional materials
* Application In scientific research or specific industrial fields, porous magnesium oxide preforms are prepared by spraying and then further processed into functional devices of desired specifications through other techniques such as melt infiltration. This is not a final coating but rather a step in the manufacturing process.
4. High-temperature electrical insulation coating
* Application In extreme environments that require high-temperature electrical insulation but where organic materials cannot be used, magnesium oxide coatings can serve as an alternative. However, the porosity of these coatings may compromise their insulating performance, typically necessitating subsequent pore-sealing treatments.
IV. More Common Applications: As an Additive for Powder Raw Materials
Magnesium oxide powder (whether spherical or not) in the field of thermal spraying—a More important, more common The role is to serve as Stabilizer additive , rather than the main spraying material.
* In zirconia ( Zirconium dioxide ) Applications in thermal barrier coatings ：
* Zirconia undergoes a phase transformation during heating and cooling, accompanied by significant volume changes that can lead to cracking and delamination of the coating.
* Add a certain proportion of Magnesium oxide ( MgO ) As a stabilizer , which can form with zirconium oxide Magnesium-stabilized zirconia ( MSZ - Magnesia-Stabilized Zirconia ) 。
* MSZ It can maintain a stable cubic phase structure at high temperatures, avoiding damage caused by phase transitions, and thus can be used as a high-performance component for parts such as engine blades. Thermal Barrier Coating ( TBC ) However, the most mainstream and highest-performing one at present is... Yttria-stabilized zirconia ( YSZ ) ， MSZ Its applications are relatively few.
Summary
Feature | Description | The impact on thermal spraying |
Extremely high melting point | 2852°C | Difficult to melt, poor adhesion strength of the coating, and prone to looseness and porosity. |
High insulation performance | Excellent high-temperature electrical insulator | Insulating coatings suitable for special operating conditions. |
Alkali resistance | High resistance to erosion by alkaline slag | Suitable for specific corrosive environments. |
Easily soluble in acid | Soluble in most acids except hydrofluoric acid. | Can be used as “ Sacrificable ” The barrier layer. |
Spherical powder | Good liquidity, stable powder delivery. | It is a prerequisite for effective spraying. |
Conclusion:
Thermal Spraying Spherical Magnesium Oxide Powder Non-mainstream wear- and corrosion-resistant coating materials Its primary value lies in:
1. Special functional applications Such as high-temperature thermal insulation, removable sacrificial layers, and high-temperature insulation.
2. As an important additive As a stabilizer for the preparation of magnesium-stabilized zirconia. MSZ Thermal barrier coating materials.
Therefore, when selecting thermal-spray materials, unless there are very specific functional requirements (such as exceptional alkali resistance and the ability to be removed by acid pickling), other, more established ceramic materials with better and more reliable performance are usually given priority.
Online Quotation
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