How does the relative density and porosity of the target affect the coating quality?

The relative density of the target is the ratio of the actual density of the target to the theoretical density, the theoretical density of the single-component target is the crystalline density, and the theoretical density of the alloy or mixture target is determined by the theoretical density of each component and its content in the alloy or mixture. proportion is calculated. The thermal spraying Tungsten Sputtering Target has a loose and porous structure, high oxygen content (even if it is vacuum sprayed, it is difficult to avoid the generation of oxides and nitrides in the alloy target), the surface is gray, lacks metallic luster, and the adsorbed impurities and moisture are the main The source of pollution, which hinders the rapid acquisition of high vacuum, easily leads to discharge during the sputtering process, and even burns the target.

At the same time, the instantaneous high temperature on the sputtering surface of the target can easily cause the loose particles to fall off, contaminate the glass surface, and affect the coating quality. There are clear regulations for the point-like release on the surface of coated glass. The regulations are shown in Table 1. The higher the relative density, the faster the film formation rate and the more stable the sputtering process. According to the difference of the target preparation process, the relative density of the casting target should be guaranteed to be above 98%, and the powder metallurgy target should be guaranteed to be above 97% to meet the production requirements. Therefore, it is necessary to strictly control the density of the target material to reduce the occurrence of slag removal. The spraying target has low density and low preparation cost. When the relative density can be guaranteed to be more than 90%, it generally does not affect the use. The SiA1 targets currently used are all spraying targets.

In addition to the density, if the target is abnormal in the production process, such as large particles falling off or shrinking cavities due to heat, more pores (internal defects) will be formed, and larger inside the target (casting target>2mm, spraying target> 0.5mm) or denser holes will cause discharge due to charge concentration, affecting use. Targets with low density and pores are prone to chipping during subsequent processing, handling or installation. The target material with high relative density and few pores has good thermal conductivity, and the heat on the surface of the sputtering target material is easily and quickly transferred to the inner surface of the target material or the cooling water in the liner, and the heat dissipation is good, thus ensuring the stability of the film formation process.

Titanium fittings are heat treated to remove residues

When the hydrogen content in the titanium pipe fitting is too large, the impact toughness and notched tensile strength will drop sharply due to embrittlement, so it is generally stipulated that the hydrogen content in the titanium pipe should not exceed 0.015%. In order to reduce the amount of hydrogen absorption, the parts should be free of fingerprints, rolling mill marks, grease and other residues before heat treatment, and there is no moisture in the heat treatment furnace. If the hydrogen content of titanium pipes exceeds the allowable value, it must be removed by vacuum annealing.

When the temperature does not exceed 540 degrees, the oxide film of the titanium pipe will not be significantly thickened, but at a higher heat treatment temperature, the oxidation rate will rapidly accelerate, and at the same time, the internal diffusion layer of the oxidized material is a pollution layer. The oxygen contamination layer has a high brittleness ratio that leads to cracks and damage on the surface of the part. There are mechanical processing methods, or chemical methods such as pickling, chemical milling, etc. for deoxidizing pollution layers. During heat treatment, the heating time should be shortened as much as possible under the premise of ensuring heat treatment. It can also be carried out in a vacuum furnace or an inert gas heating furnace. . The contamination of titanium pipe fittings when heated in an air furnace should be appropriately avoided or mitigated.

Application areas of titanium alloy capillaries

The capillary titanium alloy tube is atomized by pyrogen and the granules in the molten state are severely attacked at a high speed to the surface of the cleaned and unsmooth substrate to produce the required coating. The moment the particles hit the surface of the substrate hard, it will be deformed, and with the help of the "England" effect, a coating with a lamellar structure is produced. With many "overlapping continuous accumulation" of plastic deformation particles, the fusion between particles should be mostly mechanical equipment, and there must be a certain number of holes. In addition, if painting is carried out in the air, there is likely to be metal in the coating. Mixed oxides.

Titanium tubes are mainly used to make aero-engine compressor components, followed by rockets, cruise missiles and structural parts of high-speed airports. In the middle and late 1960s, titanium and aluminum alloys have been used in general industrial production to make electric grades for electrolytic industrial production, coolers in power plants, electric heaters for crude oil refining and seawater desalination equipment and their air pollution. Manipulating equipment, etc. ASTM F136 6Al-4V ELI Titanium Bar and aluminum alloys have become a corrosion-resistant structural raw material. In addition, it is also used to produce hydrogen storage raw materials and shape memory alloys.

Capillary titanium alloy tube is a new key structural raw material used in aerospace industry production. Its proportion, compressive strength and application temperature are close to the middle of aluminum and steel, but it has high specific strength and excellent sea surface corrosion resistance and low temperature characteristics.

Several Local Corrosion Characteristics of Titanium Materials

 1.1 Crevice corrosion The crevice corrosion resistance of titanium is particularly strong, and crevice corrosion occurs only in a few chemical media. The crevice corrosion of titanium is closely related to temperature, chloride concentration, pH value and the size of the crevice. According to relevant information, crevice corrosion is easy to occur when the temperature of wet chlorine gas is above 85 ℃. For example, in some factories, a packed tower is used to directly cool the wet chlorine gas before the cooler to reduce the temperature of the wet chlorine gas to 65-70 ℃, and then enter the titanium cooler to improve the resistance to crevice corrosion, and the effect is also very significant. Practice has proved that reducing the temperature is one of the effective methods to prevent crevice corrosion, and crevice corrosion of Grade 5 Ti-6Al-4V Titanium Wire has also occurred in high temperature sodium chloride solution. In short, for the parts and components that are prone to crevice corrosion, such as the sealing surface, the expansion joint between the tube sheet and the tube, the plate heat exchanger, the contact part between the tray and the tower body, and the fasteners in the tower, titanium such as Ti-0.2Pd should be used. Alloys, gaps and stagnation areas should be avoided in the design. For example, the fasteners in the tower should be connected with bolts as much as possible. It is better to use expansion joint and sealing welding structure for tube sheet and pipe than simple expansion joint. For flange sealing surface, asbestos gasket should not be used, but PTFE film-coated asbestos gasket should be used.

1.2 High temperature corrosion

The high temperature corrosion resistance of Grade 5 Ti-6Al-4V Titanium Sheet depends on the characteristics of the medium and the performance of its own surface oxide film. In air or oxidizing atmosphere, titanium can be used as a structural material up to 426 °C, but at about 250 °C, titanium begins to absorb hydrogen significantly. In a complete hydrogen atmosphere, when the temperature rises above 316 °C, titanium Hydrogen absorption becomes brittle. Therefore, without extensive testing, titanium should not be used in chemical equipment with a temperature higher than 330 °C. Considering hydrogen absorption and mechanical properties, the operating temperature of all-titanium pressure vessels should not exceed 250 °C. The upper limit of the use temperature of the tube is about 316°C.

1.3 Stress corrosion

Except for a few kinds of media, industrial pure titanium has excellent stress corrosion resistance, and the phenomenon of titanium equipment damage caused by stress corrosion is still rare. Industrial passive titanium is only used in fuming nitric acid, some methanol solutions or some hydrochloric acid solutions, high temperature hypochlorite, molten salt with a temperature of 300-450 ° C or NaCl atmosphere, carbon disulfide, n-hexane and dry chlorine and other media. Stress corrosion occurs. The tendency of stress corrosion cracking of titanium in nitric acid increases with the increase of NO2 content and the decrease of water content. The stress corrosion tendency of titanium reaches its maximum in anhydrous nitric acid containing 20% ​​free NO2. When the concentrated nitric acid contains more than 6.0% NO2 and less than 0.7% H2O, the stress corrosion cracking of industrial pure titanium occurs even at room temperature. Serious stress corrosion and explosion have occurred in my country when titanium equipment is used in 98% concentrated nitric acid. Industrial pure titanium is sensitive to stress corrosion cracking in 10% hydrochloric acid solution, and titanium produces stress corrosion in 0.4% hydrochloric acid plus methanol solution.

To sum up, titanium has strong corrosion resistance in acid and alkali. It can form oxide film in acid and alkali, but it is also conditional. I hope it can help you when using our materials.

Common specifications and main applications of titanium forgings such as titanium cakes and titanium rings

Titanium forgings have high strength and low density, good mechanical properties, good toughness, and corrosion resistance. In addition, the process performance of titanium forgings is poor, cutting is difficult, and it is very easy to absorb impurities such as hydrogen, oxygen, nitrogen, and carbon during hot processing. There is also poor wear resistance and a complex production process. The industrial production of titanium started in 1948. The need for the development of the aviation industry makes the titanium industry develop at an average annual growth rate of about 8%. At present, the annual output of titanium forgings in the world has reached more than 40,000 tons, and there are nearly 30 types of titanium forgings. The most widely used titanium forgings are Ti-6Al-4V (TC4), Ti-5Al-2.5Sn (TA7), and industrial pure titanium (TA1, TA2 and TA3).

F9 Titanium Forgings are mainly used to make aircraft engine compressor parts, followed by structural parts of rockets, missiles and high-speed aircraft. In the mid-1960s, titanium and its alloys have been used in general industry for making electrodes in the electrolysis industry, condensers in power stations, heaters in petroleum refining and seawater desalination, and environmental pollution control devices. Titanium and titanium alloys have become a corrosion-resistant structural material. In addition, it is also used in the production of hydrogen storage materials and shape memory alloys.

Standard: National Standard GB/T 16598-1996

American Standard: ASTM B381

Material: TA0, TA1, TA2, TA3, TC4

Delivery state: Annealed state (M) Hot working state (R) Cold working state (Y) (annealing, ultrasonic flaw detection)

Packing: carton or wooden box packing

Surface treatment: car light, chamfering

Surface quality: The surface roughness Ra value of the two end faces should not be greater than 3.2lμm (to meet the requirements of ultrasonic inspection), and the surface roughness Ra of the inner and outer sides should not be greater than 12.5μm (when ultrasonic flaw detection is required for the outer circumferential surface) Ra should not be greater than 3.2μm), the chamfer radius is 5 ~ 15mm. There should be no visible defects such as cracks, folds, and heavy skins on the surface of the product. Local defects on the surface can be removed by grinding, and the cleaning depth should not exceed its dimensional tolerance, and its minimum allowable size should be guaranteed. The ratio of cleaning depth to width should be no more than 1:6 on both ends, and no more than 1:10 on the inner and outer sides. Grinding on the outer side should follow the axial direction.

Surface finish: clean, dust-free, better acid-resistant service life.

Testing: mechanical properties, chemical composition testing, ultrasonic testing.

What is the difference between beta titanium and pure titanium

1. Different metals: pure titanium is a titanium metal material with a titanium purity of more than 99%. Beta titanium refers to a titanium material that is cooled to complete beta particles with a delay in the critical point state of titanium, not a titanium metal material.

2. Different abilities: pure titanium has a high melting point, light material, strong corrosion resistance, and firm electroplating layer. In the glasses industry, pure titanium frames often refer to frames made of a titanium material. Beta titanium has better strength, fatigue resistance, and environmental corrosion resistance than titanium pure powder, and has good shape plasticity. It can be made into wires and sheets, and it can be used to make glasses.

3. Different materials: β-titanium is a material that is relatively larger than pure titanium, but it is lighter than ordinary metals, so its purity is relatively low, about 75%, and in the process of use It has higher strength than pure titanium, and strong environmental corrosion resistance. The proportion of pure titanium reaches 89%, but the material is relatively soft.

Development status of domestic titanium strips

Titanium and titanium alloys are processed into products such as plates, strips, foils, tubes, rods, wires, forgings, castings, and composite materials. Titanium plates and strips are the most important product forms, but the processing of titanium plates and strips The process performance is poor, and the cutting process is difficult. In hot processing, it is very easy to absorb impurities such as hydrogen, oxygen, carbon, and nitrogen. At the same time, the wear resistance of the titanium plate and strip is poor, and the production process is complicated. Before 2007, the industrial production of titanium foil sheet in China was in a blank state. Titanium strips and coils were completely dependent on imports. The procurement costs were high, the cycle was long and the quality was unstable, which seriously affected the development of the downstream application fields of titanium strips and welded pipes. In recent years, many domestic enterprises represented by Hunan Xiangtou Jintian Technology Group have successively rolled hot-rolled titanium strips and cold-rolled titanium strips, the production technology of hot-rolled and cold-rolled pure titanium strips, and the heat treatment of strips. Technology, rolling process control technology, and other aspects have made great progress. With the acceleration of the construction of domestic nuclear power and PTA projects and the demand for localization, the demand for thin-walled titanium welded pipes, chemicals, and plates to replace titanium plates is becoming more and more strong. The total amount of processed materials is 59.2%, of which the output of titanium coils accounts for more than half. For applications in the field of nuclear power condensers and heat exchangers, the use of titanium coils has the advantages of high-quality stability, suitable for batch continuous production, short production cycle, and cost reduction compared with the use of block single sheets. The product has become the preferred material for welded pipes and plate heat exchangers for nuclear power.