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TiAIN Coating(2)

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Update time : 2018-08-22 15:02:20

2 Effect of doping elements on the structure and properties of TiAlN coatings
Applying a coating to the component allows the component to have superior overall mechanical properties, extend its useful life, and greatly increase efficiency. TiAlN coating has excellent wear resistance and high temperature oxidation resistance. It is widely used in the surface of dry cutting tools. With the rapid development of high speed cutting of modern tools, the performance of TiAlN coating needs to be further improved. Reasonable addition of alloying elements can effectively improve and improve the structure and properties of TiAlN coatings. This paper summarizes the effects of several common elements on the structure and properties of TiAlN coatings.

carbide drill with TiAIN coating

(1) Effect of doping element V on structure and properties of TiAlN coating
Wear resistance is the wear resistance of the material, which has a great relationship with the microstructure of the coating. The addition of V element in the TiAlN coating can improve the structure of the TiAlN coating, improve its wear resistance, corrosion resistance and thermal shock resistance. performance. When the V content in the TiAlVN coating is low, the hardness of the coating decreases with the increase of the V content, and the wear resistance is better than that of the TiAlN coating. The addition of V makes the grain of TiAlN coating finer and the structure is more compact, which can effectively prevent the failure of the coating. Different from the oxidation of TiN coating at 550 °C, both TiAlN coating and TiAlVN coating have oxidative weight gain after 750 °C. The oxidation turning point of TiAlN coating is 920 °C. The coating is rapidly oxidized and gradually exceeds 920 °C. Failure, while TiAlVN coating is still not obvious weight gain when it exceeds 1000 °C, and still has good oxidation resistance. TiAlVN coating belongs to face-centered cubic (fcc) and hexagonal close-packed (hcp) double structure, mainly including fcc AlN, TiN, VN phase and hcp AlN phase. The lattice constant is smaller than TiAlN coating, and the grain size is larger than TiAlN. When the V content is 10.20%, the TiAlVN coating quality is relatively good; the corrosion current of TiAlVN coating is significantly smaller than that of TiAlN coating, and the corrosion resistance is enhanced. The corrosion resistance of TiAlVN coating containing V10.20% is about 4 times the TiAlN coating.
(2) Effect of doping element Cr on the structure and properties of TiAlN coating
The Cr element is added to the TiAlN coating to form a strong Al-Cr bond, forming a face-centered cubic structure with a certain preferred part on the (111) and (200) faces, which has a high bonding force and can effectively reduce the coating. The friction coefficient improves the wear resistance, high temperature oxidation resistance and corrosion resistance, but the Cr content is too low or too high, which will adversely affect the mechanical properties of the coating. The addition of Cr refines the grain of Ti0.3Al0.55Cr0.15N coating. At high temperature oxidation, Cr not only promotes the formation of a stable Al2O3 oxide film on the surface of the coating, but also inhibits the anatase TiO2 to rutile TiO2. The transformation can also improve the oxidation resistance of the Al-depleted region; finally, a dense Cr2O3 and TiO2 oxide film can be formed inside, and finally the substrate is well protected. The high temperature oxidation resistance can be increased by 150 ° C compared to the TiAlN coating.
(3) Effect of doping element Si on corrosion resistance of TiAlN coating
The Si element is added to the TiAlN coating, and the TiAlSiN coating formed is of a NaCl structure and exhibits a (200) preferred part. The Si element can exist in the form of a stable amorphous phase of Si3N4 and the Si element is insoluble in TiAlN to form a nc-TiAlN/α-Si3N4 nanocomposite structure encapsulating TiAlN. This nanocomposite structure produces a strengthening effect and produces a hardness. An important influence, the addition of Si in TiAlN can increase its hardness from 35.7 GPa to 42.4 GPa. The TiAlSiN coating exhibits good thermal stability. The addition of Si reduces the critical content of Al in the transition from B1 to B4. The stable amorphous phase of Si3N4 can hinder the steady phase h during annealing. -AlN formation. When the Si content in the coating is 10 at%, the TiAlN coating exhibits a face-centered cubic, close-packed hexagonal mixed structure. The interfacial effect of the nc-TiAlN/α-Si3N4 structure in the coating effectively prevents thermal decomposition at high temperatures. After annealing at 1100 °C, the TiAlSiN coating can still exhibit a hardness of 39.7 GPa. The addition of Si increases the oxidation temperature of the TiAlN coating from 850 ° C to about 1100 ° C. At cutting speeds of 160 m/min and 200 m/min, the life of TiAlSiN coated inserts is 17% and 24% higher than that of TiAlN coated inserts.
The TiAlSiN tool coating prepared by Swiss PLAITT has a coating hardness of 50 GPa and is extremely excellent in thermosetting. When the temperature is 1200 ° C, the hardness can still be maintained at about 30 GPa. The structure of the TiAlSiN coating affects its performance, which in turn affects its use. Compared with the traditional TiAlN tool coating, TiAlSiN coating not only can extend tool life, improve processing efficiency, but also has better wear resistance, corrosion resistance and oxidation resistance. The characteristics of TiAlSiN coating make it cut in the tool. It plays an increasingly important role in the field of processing applications.

(4) Effect of doping element Y on corrosion resistance of TiAlN coating
The crystal structure of TiAlYN coating is NaCl structure, the lattice constant range is 0.4191-0.4213, and it has a preferred part. When the Y element exceeds a certain amount, the face-centered cubic structure in the coating will transform to the close-packed hexagonal structure, so that the coating structure The stability of the decline. In the coating, as the Y content increases, the lattice constant decreases, the increase of the coherent scattering size and the reduction of the surface roughness can refine the grain, reduce the structural defects such as holes in the coating, and make the coating more Dense, improve the hardness and wear resistance of the coating and the adhesion between the coating and the substrate, while improving the adhesion of the Al2O3 oxide film to the substrate during high-temperature oxidation, effectively preventing further oxidation of the coating and increasing the high temperature resistance of the coating. Oxidation ability. Among the many alloying addition elements, Y element is one of the most significant elements to significantly improve the high temperature oxidation performance of the coating. When the addition amount of Y is about 1 at%, the hardness of Ti0.5-xAl0.5YxN coating is between 32-36 GPa, and the addition of Y element to form dense non-columnar crystal nano-structure fine particles significantly reduces the surface roughness. Reduce internal stress, thereby improving the wear resistance of the coating by 3-5 times. Within 10 h of oxidation at 850 °C, the surface oxide grains of TiAlYN are finer and the thickness of the oxide film is less than half of the former. Adding Y can reduce the number of droplets on the surface of the film and improve the oxidation resistance of the film.
(5) Effect of doping element B on corrosion resistance of TiAlN coating
The addition of B to the TiAlN coating results in the formation of TiB2 and BN phases in the surface of the coating. Due to the high hardness of TiB2, the friction coefficient of BN is small. During the processing, TiAlBN easily forms BN and BN3 through the diffusion of B, thus obtaining Conducive to the processing of the lubricating film layer, improve the friction and wear properties of the coating. The TiAlBN coating deposited on the stainless steel substrate by ion beam evaporation includes three phases of nc-(Ti,Al)N, a-BN, a-(Ti,Al)B2, wherein the Al content is maintained at 4-7at. In the (Ti,Al)B029N0.46 film system, there are 72-79 mol% of nc-(Ti,Al)(N,B)1-x phase and 21-28 mol% of amorphous content. Titanium boride has a microhardness of 22-32 GPa and a preferred part of (111) plane. The addition of element B can refine the grains but reduce the density and hardness of the coating.
The effect of alloying elements on the results and properties of TiAlN coatings is significant. Among them, the content of Si has a great influence on the hardness of the coating and the bond strength of the film. Within a certain range, the hardness of the coating increases with the increase of Si content. The film-based bonding force is increased. Si element also has the effect of improving oxidation resistance, wear resistance, corrosion resistance and tool life. At present, the addition of Si element in TiAlN coating has attracted extensive attention in the academic community. The addition of V can greatly reduce the oxidation rate, thereby effectively improving the oxidation resistance of the coating, and at the same time improving the wear resistance and corrosion resistance of the TiAlN coating. The addition of Cr and Y elements can refine the crystal grains, and can improve the hardness, wear resistance and film-based bonding force of the TiAlN coating, and can also significantly improve the high temperature oxidation resistance. The addition of B element to the TiAlN coating can greatly improve its anti-wear performance and achieve the effect of reducing friction and reducing wear.
TiAlN hard coating has high hardness, corrosion resistance, high temperature oxidation resistance and high wear resistance, but the requirements of modern processing technology are getting higher and higher. TiAlN based coating still needs to continue to improve and improve its comprehensive performance by adding The alloying elements and the application of the layered composite coating optimize the structure of the coating and improve the toughness of the coating to accommodate a variety of complex cutting conditions. In addition to the current alloying of TiAlN-based coatings, it is also possible to develop nano-multilayer and nano-composite coatings, multi-layer multi-layer alloy composite coatings, and tool soft coatings with special properties. It will be an important research direction in the field of tool coating in the future.