Boron Nitride: An Emerging Force in The Coating Field
May 16, 2025
Property Basis of Boron Nitride
High Hardness and Wear Resistance
Cubic boron nitride has a hardness second only to diamond, with a Vickers hardness reaching 5000 - 8000HV. This characteristic enables the film layer formed by incorporating c-BN in coating to effectively resist external friction and wear. In the field of tool coating, when a tool surface is coated with a c-BN-containing layer, during high-speed cutting of metallic materials, the coating can significantly reduce the friction coefficient between the tool and the workpiece, minimize tool wear, and greatly extend the tool's service life and improve cutting efficiency. For example, when machining high-hardness alloy materials, ordinary tools may experience severe wear in a short time, while tools coated with c-BN can maintain a sharp cutting edge, enabling continuous and stable machining, and significantly enhancing machining precision and surface quality.
Chemical Stability
Hexagonal boron nitride exhibits excellent chemical stability and hardly reacts with molten metals. In the vacuum coating process, the evaporation boat, as a core consumable, needs to operate stably under high temperatures (＞1500°C), in highly corrosive metal melts (such as aluminum and copper), and in a high-vacuum environment. Traditional graphite evaporation boats are vulnerable to erosion by molten metals and have a short service life. In contrast, h-BN-based ceramic materials have become an ideal alternative due to their chemical stability. h-BN evaporation boats can prevent boat body corrosion, avoid coating contamination caused by boat body corrosion, and ensure the stability of the coating process and the reliability of the coating quality.
High Thermal Conductivity and Low Thermal Expansion Coefficient
Boron nitride has a high in-plane thermal conductivity. For instance, h-BN powder can form an excellent horizontally oriented thermal conduction network during the preparation of evaporation boats, with an in-plane thermal conductivity ＞250 W/(m·K). Meanwhile, its thermal expansion coefficient is extremely low. During the coating process, especially in some processes that involve rapid heating and cooling cycles, the coating material needs to withstand drastic temperature changes. The high thermal conductivity and low thermal expansion properties of boron nitride ensure uniform heat distribution, effectively withstand repeated rapid heating and cooling shocks during the coating process, prevent film cracking, and maintain the integrity and performance stability of the film layer. For example, in the coating process of semiconductor chip manufacturing, which has extremely high requirements for the thermal stability of the film layer, boron nitride coatings can meet these stringent requirements, providing a stable and reliable foundation for chip manufacturing.
Applications of Boron Nitride in Different Coating Processes
Physical Vapor Deposition (PVD)
In the PVD process, boron nitride is often used to prepare hard coatings. Take multi-arc ion plating as an example. The metal evaporation source serves as the cathode, and through arc discharge between it and the anode shell, the target material evaporates and ionizes to form a spatial plasma for depositing the coating on the workpiece. When a boron nitride target is used, the deposited boron nitride coating has extremely high density and adhesion. This coating has a high hardness, more than three times that of die steel, and can even reach over 5000HV; it is fine and smooth, with a low friction coefficient with steel; it does not easily adhere to metals, preventing chip build-up and improving the surface quality of the machined parts; it also has good toughness, impact resistance, and collision resistance, and can be applied to die-casting molds, stamping molds, etc. For example, in the manufacturing of automotive parts, after coating some molds with boron nitride, the mold's wear resistance is significantly enhanced, the surface quality of the produced parts is improved, the mold maintenance and replacement frequency is reduced, and production efficiency and economic benefits are greatly increased.
Chemical Vapor Deposition (CVD)
The CVD method has unique advantages in preparing boron nitride thin films, such as a simple preparation process, high-quality films, and large growth areas. When preparing thin films for metal surface corrosion protection, CVD-prepared boron nitride thin films can be directly used for metal corrosion protection. h-BN, similar to the planar network structure of graphite, is commonly known as "white graphene" and has excellent properties such as good insulation, high thermal stability, and strong chemical stability. A single-layer defect-free boron nitride has excellent shielding performance, which can block corrosion factors such as oxygen and water molecules from reaching the metal substrate surface and inhibit electron transfer, thereby reducing the possibility of galvanic corrosion of the base metal. However, CVD-prepared boron nitride thin films inevitably have grain boundaries and defects. By combining with atomic layer deposition, metal oxide particles can be uniformly distributed at the vacancies, grain boundaries, and wrinkled defects of the boron nitride film layer and on the surface to form a boron nitride composite film, which can significantly improve the corrosion resistance of metals and achieve long-term protection of the base metal.
Application Cases and Effects
Application Case of Tool Coating
A tool manufacturing enterprise applied c-BN coating technology to its milling cutter products. During the milling test of high-strength alloy steel, the uncoated ordinary milling cutter showed obvious edge wear after machining 100 workpieces, resulting in a decrease in machining precision and an increase in workpiece surface roughness. In contrast, the c-BN-coated milling cutter exhibited minimal wear after machining the same number of workpieces, and its cutting edge remained sharp, enabling continuous and stable high-precision machining. Further tests showed that the service life of the c-BN-coated milling cutter was more than five times that of the ordinary milling cutter, significantly reducing tool replacement costs, improving machining efficiency, and bringing remarkable economic benefits to the enterprise.
Application Case of Metal Corrosion Protection Coating
An aerospace component manufacturing company adopted boron nitride composite film coating technology to improve the corrosion resistance of aluminum alloy components in complex environments. After surface treatment of the aluminum alloy components, h-BN thin films were deposited by the CVD method, and then a uniform metal oxide film was coated on the h-BN thin films by atomic layer deposition to form a boron nitride composite film. After various simulated harsh environment tests, such as salt spray corrosion tests and damp heat aging tests, the results showed that the uncoated aluminum alloy components showed obvious corrosion spots after 24 hours in a salt spray environment, while the components coated with the boron nitride composite film remained intact without any signs of corrosion after 1000 hours of salt spray testing. The application of this technology effectively enhances the reliability and service life of aerospace components and ensures the safe operation of aircraft in complex environments.
Property Basis of Boron Nitride
High Hardness and Wear Resistance
Cubic boron nitride has a hardness second only to diamond, with a Vickers hardness reaching 5000 - 8000HV. This characteristic enables the film layer formed by incorporating c-BN in coating to effectively resist external friction and wear. In the field of tool coating, when a tool surface is coated with a c-BN-containing layer, during high-speed cutting of metallic materials, the coating can significantly reduce the friction coefficient between the tool and the workpiece, minimize tool wear, and greatly extend the tool's service life and improve cutting efficiency. For example, when machining high-hardness alloy materials, ordinary tools may experience severe wear in a short time, while tools coated with c-BN can maintain a sharp cutting edge, enabling continuous and stable machining, and significantly enhancing machining precision and surface quality.
Chemical Stability
Hexagonal boron nitride exhibits excellent chemical stability and hardly reacts with molten metals. In the vacuum coating process, the evaporation boat, as a core consumable, needs to operate stably under high temperatures (＞1500°C), in highly corrosive metal melts (such as aluminum and copper), and in a high-vacuum environment. Traditional graphite evaporation boats are vulnerable to erosion by molten metals and have a short service life. In contrast, h-BN-based ceramic materials have become an ideal alternative due to their chemical stability. h-BN evaporation boats can prevent boat body corrosion, avoid coating contamination caused by boat body corrosion, and ensure the stability of the coating process and the reliability of the coating quality.
High Thermal Conductivity and Low Thermal Expansion Coefficient
Boron nitride has a high in-plane thermal conductivity. For instance, h-BN powder can form an excellent horizontally oriented thermal conduction network during the preparation of evaporation boats, with an in-plane thermal conductivity ＞250 W/(m·K). Meanwhile, its thermal expansion coefficient is extremely low. During the coating process, especially in some processes that involve rapid heating and cooling cycles, the coating material needs to withstand drastic temperature changes. The high thermal conductivity and low thermal expansion properties of boron nitride ensure uniform heat distribution, effectively withstand repeated rapid heating and cooling shocks during the coating process, prevent film cracking, and maintain the integrity and performance stability of the film layer. For example, in the coating process of semiconductor chip manufacturing, which has extremely high requirements for the thermal stability of the film layer, boron nitride coatings can meet these stringent requirements, providing a stable and reliable foundation for chip manufacturing.
Applications of Boron Nitride in Different Coating Processes
Physical Vapor Deposition (PVD)
In the PVD process, boron nitride is often used to prepare hard coatings. Take multi-arc ion plating as an example. The metal evaporation source serves as the cathode, and through arc discharge between it and the anode shell, the target material evaporates and ionizes to form a spatial plasma for depositing the coating on the workpiece. When a boron nitride target is used, the deposited boron nitride coating has extremely high density and adhesion. This coating has a high hardness, more than three times that of die steel, and can even reach over 5000HV; it is fine and smooth, with a low friction coefficient with steel; it does not easily adhere to metals, preventing chip build-up and improving the surface quality of the machined parts; it also has good toughness, impact resistance, and collision resistance, and can be applied to die-casting molds, stamping molds, etc. For example, in the manufacturing of automotive parts, after coating some molds with boron nitride, the mold's wear resistance is significantly enhanced, the surface quality of the produced parts is improved, the mold maintenance and replacement frequency is reduced, and production efficiency and economic benefits are greatly increased.
Chemical Vapor Deposition (CVD)
The CVD method has unique advantages in preparing boron nitride thin films, such as a simple preparation process, high-quality films, and large growth areas. When preparing thin films for metal surface corrosion protection, CVD-prepared boron nitride thin films can be directly used for metal corrosion protection. h-BN, similar to the planar network structure of graphite, is commonly known as "white graphene" and has excellent properties such as good insulation, high thermal stability, and strong chemical stability. A single-layer defect-free boron nitride has excellent shielding performance, which can block corrosion factors such as oxygen and water molecules from reaching the metal substrate surface and inhibit electron transfer, thereby reducing the possibility of galvanic corrosion of the base metal. However, CVD-prepared boron nitride thin films inevitably have grain boundaries and defects. By combining with atomic layer deposition, metal oxide particles can be uniformly distributed at the vacancies, grain boundaries, and wrinkled defects of the boron nitride film layer and on the surface to form a boron nitride composite film, which can significantly improve the corrosion resistance of metals and achieve long-term protection of the base metal.
Application Cases and Effects
Application Case of Tool Coating
A tool manufacturing enterprise applied c-BN coating technology to its milling cutter products. During the milling test of high-strength alloy steel, the uncoated ordinary milling cutter showed obvious edge wear after machining 100 workpieces, resulting in a decrease in machining precision and an increase in workpiece surface roughness. In contrast, the c-BN-coated milling cutter exhibited minimal wear after machining the same number of workpieces, and its cutting edge remained sharp, enabling continuous and stable high-precision machining. Further tests showed that the service life of the c-BN-coated milling cutter was more than five times that of the ordinary milling cutter, significantly reducing tool replacement costs, improving machining efficiency, and bringing remarkable economic benefits to the enterprise.
Application Case of Metal Corrosion Protection Coating
An aerospace component manufacturing company adopted boron nitride composite film coating technology to improve the corrosion resistance of aluminum alloy components in complex environments. After surface treatment of the aluminum alloy components, h-BN thin films were deposited by the CVD method, and then a uniform metal oxide film was coated on the h-BN thin films by atomic layer deposition to form a boron nitride composite film. After various simulated harsh environment tests, such as salt spray corrosion tests and damp heat aging tests, the results showed that the uncoated aluminum alloy components showed obvious corrosion spots after 24 hours in a salt spray environment, while the components coated with the boron nitride composite film remained intact without any signs of corrosion after 1000 hours of salt spray testing. The application of this technology effectively enhances the reliability and service life of aerospace components and ensures the safe operation of aircraft in complex environments.
Shengyang New Material Co., Ltd. is committed to the production of boron nitride and boron nitride processed products, and can customize various boron nitride insulating ceramic parts according to customer needs. Contact us if necessary.
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