Titanium Nitride (TiN) is a compound formed by the reaction of titanium and nitrogen. It is golden or metallic, hard and wear-resistant, and has excellent chemical stability and high temperature resistance. It is a very important hard coating material, widely used in metal processing, tool manufacturing, automotive industry, aerospace, medical equipment and other fields. In the machining industry, TiN coating is used to improve the service life and processing efficiency of tools, especially under high load and high temperature environments.
Definition and characteristics of TiN coating
1. Definition of TiN coating
Titanium nitride (TiN) is used in PVD (physical vapor deposition) process using transverse rotating cathode technology. The material evaporates from a solid source in the form of atoms/molecules, and then is transported to the substrate in the form of vapor through vacuum low-pressure gas/plasma and condensed on the substrate.
2. Physical and chemical properties of TiN coating
Hardness: The hardness of TiN coating is as high as about 2000 HV (Vickers hardness), which significantly improves the wear resistance and durability of the substrate.
Wear resistance: TiN coating has extremely strong wear resistance, which can significantly extend the service life of tools or parts and reduce wear and scratches.
High temperature resistance: TiN coating has very good temperature resistance and can withstand temperatures up to 500-600°C, suitable for high temperature working environments.
Corrosion resistance: TiN has good corrosion resistance and can resist the erosion of acids, alkalis and salt water, and is suitable for harsh chemical environments.
Chemical stability: TiN has good chemical stability and is not easy to react with other chemicals. It is widely used in environments with precision machining and chemical corrosion resistance requirements.
Friction coefficient: TiN coating reduces the friction coefficient of metal surfaces, helps to reduce friction and heat generation between parts, and thus improves the use efficiency of parts.
Appearance: TiN has a golden or metallic gold color, and its brightness and glossiness are very high, which increases the aesthetics. It is often used for workpiece surfaces that require beauty and functionality, such as high-end jewelry, watch parts, automotive accessories, etc.
Low surface energy: The surface energy of TiN coating is low, which can effectively reduce the adhesion of cutting fluid and workpiece during processing, reduce wear and tool adhesion during processing.
Environmental protection: PVD and CVD technologies do not produce harmful exhaust gas or pollutants when depositing TiN coatings, so they perform well in environmental protection.
3. Disadvantages of TiN coatings
Coating brittleness: Although TiN coatings have high hardness, their high hardness also makes the coatings more fragile and prone to falling off or peeling, especially when subjected to large impact or bending stress.
Coating thickness limit: Due to the slow coating deposition speed of PVD and CVD technologies, the thickness of TiN coatings is usually between a few microns and tens of microns, which is not suitable for applications that require thicker coatings.
High cost: The deposition process of TiN coatings is relatively complex and the cost is relatively high, so they are mainly used in high-end applications or high-value components.
Preparation process of TiN coating
There are two main methods for preparing TiN coating: physical vapor deposition (PVD) and chemical vapor deposition (CVD). Among them, PVD is the most commonly used process. The following will introduce these two common TiN coating preparation methods respectively.
1. Physical vapor deposition (PVD)
PVD is a method that converts solid materials into gaseous state through physical process and deposits them on the surface of substrate to form a thin film. PVD process is widely used in the preparation of TiN coating. Common PVD technologies include evaporation deposition, magnetron sputtering and arc evaporation.
(1) Evaporation deposition method: By heating titanium metal or titanium alloy, titanium vapor is evaporated, and reacts with nitrogen in a high vacuum environment to form TiN coating.
(2) Magnetron sputtering method: Using magnetron sputtering equipment, the titanium target is bombarded with high-energy ions to release titanium atoms, which react with nitrogen molecules in a nitrogen atmosphere and are deposited on the surface of the substrate to form a TiN film.
(3) Arc evaporation method: The titanium target is heated by arc discharge, so that the titanium target material evaporates and reacts with nitrogen to deposit a TiN coating.
The PVD method can produce high-quality, uniform coatings, and the process conditions are mild, which is suitable for various substrates.
2. Chemical vapor deposition (CVD)
CVD is a method of depositing a coating on the surface of a substrate by chemical reaction using gaseous precursors. In the CVD process, titanium source and nitrogen source gases are introduced into the reaction chamber, and react after heating or plasma excitation to form a TiN coating.
(1) Low-pressure chemical vapor deposition (LPCVD): A chemical reaction is carried out under a low-pressure environment to deposit a high-quality TiN coating, which is suitable for mass production.
(2) Atmospheric pressure chemical vapor deposition (APCVD): Deposition is carried out under atmospheric pressure conditions, which is suitable for some special applications, but due to the high temperature required, it is often used for large-sized parts or workpieces that require thicker coatings.
Although the CVD process can produce thicker coatings, it requires a higher temperature and has higher equipment requirements. Therefore, in some cases, the PVD process is more commonly used.
Application fields of TiN coating
The wide application of TiN coating not only improves the performance of tools, but also promotes the development of technology in many industries. The following are the main application fields of TiN coating:
1. Cutting tools
TiN coating is often used on metal cutting tools such as knives, drills, and milling cutters to improve their wear resistance and high temperature resistance. TiN coating can reduce friction during cutting and reduce heat accumulation between the tool and the workpiece, thereby extending the service life of the tool and improving processing efficiency.
2. Precision molds
TiN coating can improve the wear resistance of the mold surface, reduce friction between the mold and plastic or metal, and reduce the wear rate of the mold, especially in plastic molds and aluminum alloy die-casting molds.
3. Medical devices
TiN coating has important applications in medical devices, especially in surgical knives, dental tools, surgical instruments and other fields. TiN coating can improve the wear resistance and biocompatibility of the instrument, and at the same time, due to its golden appearance, it increases the aesthetics of the instrument.
4. Automotive parts
TiN coating is often used on key parts such as engine parts and automotive brake systems to improve wear resistance, high temperature resistance and corrosion resistance, extend the service life of parts and improve overall performance.
5. Decorative coating
Due to its beautiful golden luster, TiN coating is also widely used in decorative parts such as high-end accessories, watches, jewelry and mobile phone cases, combining beauty and functionality.
Development trend of TiN coating
1. Multifunctional coating: Research and develop new TiN-based composite coatings, such as TiAlN, TiSiN, etc., to improve the comprehensive performance of coatings.
2. Low-temperature coating technology: Develop low-temperature TiN coating technology to reduce the thermal impact on the substrate and expand its application range.
3. Nano-TiN coating: Use nanotechnology to manufacture more delicate and uniform TiN coatings to improve the hardness and wear resistance of the coating.
TiN coatings are widely used in machining, medical, automotive and other industries due to their excellent hardness, wear resistance, high temperature resistance and corrosion resistance. With the advancement of coating technology, the performance and application areas of TiN coatings will be further expanded. Through continuous innovation and optimization of production processes, TiN coatings will provide the industry with more efficient and economical solutions, and promote the development of machining towards higher precision and higher performance.
