The advantages of titanium alloy
Titanium alloy compared with industrial pure titanium has the following three advantages:
A, both of the oxidizing medium have excellent corrosion resistance; and weak reducing medium has a certain corrosion resistance. Such as Ti-0.2Pa corrosion resistance of nitric acid and industrial pure titanium as good; but dilute hydrochloric acid and dilute sulfuric acid corrosion resistance than pure titanium high 500-1000 times.
B, has better resistance to crevice corrosion. Industrial titanium is more susceptible to crevice corrosion, which is often accelerated by the presence of gaps in titanium equipment. Crevice corrosion can be eliminated if Ti- (0.15-0.2) Pa is used instead of commercial pure titanium in the gaps.
C, hydrogen absorption capacity is difficult to produce hydrogen embrittlement. Industrial pure titanium can absorb hydrogen in extreme temperature. Especially for atomic hydrogen generated during corrosion more easily absorbed, resulting in hydrogen embrittlement Ti- (0.1-0.20) Pa oxide film surface has a high resistance to hydrogen penetration, so anti-hydrogen embrittlement than industrial titanium to be large many.
However, this is not resistant to strongly reducing media; it also contains palladium, a precious metal. Its physical, mechanical properties, processing technology and similar properties of industrial titanium. Currently used in this alloy tube heat exchanger, used in dilute hydrochloric acid and phosphoric acid; in the textile industry to use it to make spinneret; acetaldehyde and triumphalism acid device in all flanges of titanium equipment Ring and diamond gasket are also used in this alloy, the use of good results.
Ti-Pa alloy is mainly used for dilute sulfuric acid, hydrochloric acid, phosphoric acid environment; also used for titanium equipment to prevent crevice corrosion. Under the environment of sulfuric acid, hydrochloric acid and phosphoric acid, the corrosion rate increases when the content of Pa is lower than 0.05%, while the corrosion rate almost does not change when the content is higher than 0.20%.
Ti-0.3Mo-0.8Ni alloy
This alloy improves the corrosion resistance of corrosion resistance in reducing media; and it maintains the corrosion resistance of industrial pure nitrides, chromic acid and other oxidizing media. For example, it has good corrosion resistance at room temperature 10% sulfuric acid, 10% hydrochloric acid and medium concentrations of formic acid and citric acid. It contains less alloying elements; in particular does not include rare palladium. Therefore, its price is only about 10% higher than industrial pure titanium, its processing performance, welding process performance and industrial pure titanium close; and 200-300 temperature 1.5-2 times higher than the industry pure titanium. Because of this advantage, this alloy can replace industrial grade titanium for use in elevated temperature seawater, brine, wet chlorine and high temperature and high chloride concentrations.
Ti-Mo alloy
The corrosion resistance of Ti-32Mo alloy in boiling 40% sulfuric acid and 20% hydrochloric acid solution is much higher than that of commercial pure titanium. It is part of the most corrosion-resistant titanium alloys currently available.
However, its corrosion resistance in oxidizing media is low
And molybdenum content is too high. The alloy becomes brittle, the processing performance deteriorates. In order to surmount the shortcomings of this alloy due to the high molybdenum content, Nb, V, Zr and Pa are added to the Ti-Mo alloy. This alloy not only maintains the excellent corrosion resistance of the Ti-Mo alloy, but also improves the treatment performance of the alloy. For instance, the Ti-15Mo-5Zr alloy not only avoids the alloy embrittlement caused by the ω-phase precipitation in the Ti-15Mo alloy, improves its cold workability and weldability, but also improves the corrosion resistance of the alloy. In another example, Ti-15Mo-0.2Pa alloy has excellent corrosion resistance in oxidizing and reducing media.
Ti-2Ni alloy
This Ti alloy desalination equipment as a structural material, the use of temperature up to about 200, and industrial pure titanium can only reach about 120. And its resistance to crevice corrosion is preferable to industrial pure titanium. However, the use of this alloy than Ti-Pa, Ti-Mo alloy much narrower. It is only in the formic acid, boiling concentrated solution of magnesium chloride corrosion resistance than industrial pure Ti is superior; but in hydrochloric acid, sulfuric acid corrosion worse than pure titanium. Therefore, Ti-2Ni alloy is generally limited to the use of neutral or 偌 decreasing salt solution.
Ti-6Al-4V (TC4) alloy
This is a widely used Ti alloy. Its corrosion resistance is slightly worse than that of commercially pure titanium, but it still has satisfactory corrosion resistance to seawater, many acids, alkalis and other corrosive media. It has superior overall mechanical properties. Therefore, this alloy is generally used in demanding high-strength or superior fatigue performance of the occasion.
Ti passivation film so that the medium can be in a stable titanium corrosion resistant medium. These media are oxidative, neutral, weakly reducing.
A variety of media that destroy the passivation film of Ti are titanium non-corrosion resistant media. These media are strongly reducing acids and strong anhydrous oxidants.
The order of corrosion resistance of TA0, BT1-0, Ti-0.2Pa and Zr-O in the 5% hydrochloric acid solution is Zr-O, Ti-0.2Pa, TA0 and BT1-0.
