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TiAIN Coating

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Update time : 2018-08-17 14:19:48
The rapid development of modern manufacturing has put forward higher requirements on the cutting speed and precision of cutting tools. Hard coating with excellent wear resistance and high temperature oxidation resistance is one of the effective ways to improve the performance of cutting tools. TiN and TiC coatings are the first hard coatings applied to tool surfaces. In recent years, tool coatings have been greatly developed in composition, and coating preparation processes have become increasingly mature. Among them, the ternary nitride coating with better wear resistance and oxidation resistance has been extensively researched and developed rapidly. Table 1 shows the performance of three commonly used tool surface coatings. Compared with TiN, TiAlN coating is more suitable for high-speed cutting of high alloy steel, stainless steel, titanium alloy and nickel alloy.
TiAIN coating for carbide end mill
TiAlN coatings have better mechanical properties than coatings such as TiN and TiCN, and can be combined with other coatings to form multi-layer composite coatings. The addition of Al to the TiN coating acts as a fine-grained reinforcement. A thin layer of amorphous Al2O3 is formed on the surface of the coating during the cutting process. As a hard inert protective film, it plays an important role in high-speed machining. effect. Dry and semi-dry cutting is one of the development trends of the future cutting process. For dry cutting, the tool coating can form a thermal barrier between the workpieces to reduce the thermal stress acting on the tool base. It acts as a solid lubricant to reduce the adhesion of the chips, and the TiAlN coating can well meet the above requirements. Studies have shown that the addition of refractory or semi-refractory elements (such as Al, Si, Cr, V, etc.) to the TiN coating can form a solid solution strengthening or second phase, and the surface of the film is easily formed into a chemical transfer film during the rubbing process. The wear resistance of the layers, especially at high temperatures and high loads, is more important for the lubricity of these chemical transfer films. This paper aims to summarize the research progress of diversified TiAlN-based coatings at home and abroad and the influence of doping elements on the structure and properties of TiAlN coatings.

1.
TiAlN coating and its properties
The addition of Al can improve the oxidation resistance of TiN coated tools. The oxidation temperature of TiAlN coating can reach 800 °C. The addition of Al forms an amorphous, low oxygen diffusion coefficient Al2O3 film during the cutting process, thus improving the tool. The oxidation resistance temperature; at the same time, the addition of Al forms a single-phase metastable (Ti, Al) N, which significantly improves the mechanical properties of the coating. At high temperature continuous cutting, its lifetime is about 4 times that of the TiN coating. Its good performance has received extensive attention and attention in recent years. Scholars have used reactive magnetron sputtering, arc ion plating, ion beam focusing deposition to prepare TiAlN coatings.

The deposition process has an important influence on the microstructure and properties of the TiAlN coating. The gold plow is coated with TiAlN on the surface of the high speed steel substrate (W18Cr4V) by multi-arc ion plating. The results show that the Ti target current is 80A, the Al target current is 70A, the substrate temperature is 500°C (high speed steel), the negative bias voltage is 100V, and the nitrogen partial pressure is 1.0. Pa, TiAlN coating has the best comprehensive performance at 60 min deposition time. The coating contains a certain amount of (Ti2,Al)N phase in addition to the (Ti,Al)N phase. Hu Zhijie and other TiAlN coatings on TC4 titanium alloy substrates have a negative bias voltage of 250V-400V, a duty ratio of 50%-60%, a N2 flux of 138ml/min, and a deposition temperature of 100-300°C. The time is 270min, the Ti target arc current is 50-70A, the furnace body vacuum is 10-2Pa grade, the coating thickness is 2.5-3.0μm, the microhardness is 2300-2700HV, and the comprehensive performance is good. Jiang Tao used multi-arc ion plating technology to prepare TiAlN/TiN film on the surface of common gear steel (40Cr). The results show that the substrate negative bias has a great influence on the performance of the film. Excessive or too low substrate bias will make The surface of the film is not flat and the surface microhardness is reduced. The higher the negative bias of the substrate, the lower the content of Ti and Al atoms in the film. The target current also has a significant effect on the film properties. The higher the current, the less the surface of the film. The microhardness increases first and then decreases with the increase of the target current; the content of Ti and Al atoms in the film increases with the increase of current. The increase of N2 partial pressure is beneficial to improve the surface morphology of the film. However, the excessive N2 partial pressure will cause “nitrogen poisoning” on the target surface, which will reduce the microhardness of the film and decrease the content of Ti and Al atoms in the film. . Cao Ya summarized the research status and development trend of multi-arc ion plating TiAlN coating. The multi-arc ion plating TiAlN coating can improve the coating structure and improve the strength, bonding strength and wear resistance due to the introduction of Al element.