JPS61194142A - Titanium alloy having superior corrosion resistance - Google Patents

Abstract

PURPOSE:To improve the resistance to corrosion by nonoxidizing acids and to crevice corrosion by adding a prescribed percentage of Pd, Ni, W or Mo. CONSTITUTION:This Ti alloy consists of, by weight, one or more among 0.005-2% Pd, 0.01-2% Ni, 0.005-0.5% W and 0.01-1% Mo and the balance Ti. The alloy has superior durability in an environment contg. nonoxidizing acids and superior resistance to crevice corrosion caused in a soln. contg. chlorine ions.

Description

[Detailed Description of the Invention] Due to its excellent corrosion resistance, titanium has come to be widely used as an industrial material in place of conventional corrosion-resistant metals. , or chlorate, etc., does not exhibit excellent effects.

Therefore, Ti-P is an existing alloy that improves this point.
d alloy, Ti-Ni alloy, Ti-N1-M0 alloy (patent application Sho-37455), etc. are used in some cases, but Ti-Pd alloy is expensive because it uses expensive palladium. Ti-N has the disadvantage of being expensive.
Currently, the i-alloy and the Ti-IJi-Mo alloy have not been widely used because they have the disadvantage of poor workability.

Although titanium has excellent corrosion resistance, it still poses many problems in harsh corrosive environments, and at the same time titanium alloys with some improvements have been developed to address these problems. However, it has many drawbacks and is not sufficient.

The present invention was discovered based on these circumstances, and is particularly effective in severe corrosive environments such as oxidizing alcohols, as well as being highly effective against crevice corrosion that often occurs in solutions containing chlorine ions. This relates to a titanium-based alloy that exhibits the following properties.

Its composition is titanium with palladium added.

Moreover, one of nickel, tungsten, and molybdenum
The feature is that more than m@ is added.

Its composition range is as follows.

Element Composition range (wt) Palladium 0005-2.0 Titanium balance In the titanium base metal of the present invention, the lower limit of palladium is 0.005
wts because if the addition amount is less than this, the improvement in corrosion resistance is small and it is not practical, so the upper limit is set at 2.0 wtqb.
The reason for this is that even if this value is exceeded, the corrosion resistance does not improve much, and furthermore, the use of expensive palladium results in an extremely high cost.

Second, let the lower limit of Kel be o, o t wtl.

If the amount added is less than this, no improvement in corrosion resistance can be expected.

The upper limit is 2. The reason why it is set as Owtl is that if it exceeds this value, the workability deteriorates significantly and manufacturing becomes difficult.

The reason why the lower limit of tungsten is set at αO05wt- is that, as in the case of nickel mentioned above, no improvement in corrosion resistance can be expected if the addition amount is less than this, and the reason why the upper limit is set at [1.5wt%] is that if it exceeds this, the workability will deteriorate. This is because the condition deteriorates significantly and manufacturing becomes difficult.

Similarly, the lower limit of molybdenum is α01 wtl.
If the addition amount is less than this, no improvement in corrosion resistance can be expected, and the reason why the upper limit is set at t Owts is that if this amount is exceeded, workability will be significantly deteriorated and there will be no improvement in corrosion resistance.

Next, we will compare the titanium alloy of the present invention with conventional corrosion-resistant titanium alloys and explain its effectiveness.

Comparative test The corrosion environments tested were: 1.1° H, So for general corrosion, 2.5° HCX, boiling state, and 5.10% Mail, pHa = 6.1. for crevice corrosion. This was done in a boiling state.

Table 1 shows the results for 11H, So4.

Pure T1 and existing corrosion-resistant titanium alloys are shown in A1 to 1I&4, and alloys of the present invention are shown in M5 to M28.

Nos. 45 to 12 are Ti-Pct-Ni alloys in which the amounts of Pd and Ni added are changed.

A decrease in the corrosion rate has already been observed when the amount of N1 added is CL 01 wtl (Mu5), and compared to conventional corrosion-resistant alloys (&
All of the values 1 to 4) are lower than those of 4). or.

Corrosion resistance tends to increase as the amount of Ni added increases, but when the amount of Ni added is 2. If it exceeds Owtl, the workability will drop significantly and manufacturing will become difficult. When the amount of Pa added was changed, the amount of Pd added was 0.01 wt% (A
A decrease in the corrosion rate has already been observed in No. 9), showing a lower value than any of the conventional corrosion-resistant alloys (No. 1 to No. 4). Furthermore, as the amount of Pd added increases, the corrosion resistance tends to increase significantly, but when the amount of Pd added is 2. The stop exceeds Owt!! It does not improve corrosion resistance and is expensive.
The use of d would result in a very high cost.

Next, I&15 to A18 are Ti-Pd-W alloys in which the amounts of Pd and W added are changed, respectively.

The wIIQh addition amount is 1005 wtl (413), which is lower than any of the conventional corrosion-resistant alloys (I & 1 to M 4) in which a decrease in corrosion rate has already been observed.

Furthermore, as the amount of W added increases, the corrosion resistance tends to increase, but when the amount of W added exceeds 15 wt-, the workability deteriorates significantly and manufacturing becomes difficult. Todoroki No. 16 to No. 18 show results in which the amount of pa added is changed, but the tendency is that T
i-P (same as in the case of 1-Ni alloy).

Next, A19 to A24 are Ti-Pa-Mo alloys in which the added amounts of P(1 and MO were changed, respectively.) When the amount of Mo added was α01 wt (Mu19), there was already a decrease in the corrosion rate. It shows a lower value than any of the conventional corrosion resistant alloys (I61 to A4).Also, as the amount of Mo added increases, the corrosion resistance tends to increase, but when the amount of Mo added is t Owt - If the amount exceeds -, the workability will drop significantly and manufacturing will become difficult, and the corrosion resistance will not improve much.
Figures 22 to A24 show that the tendency is Ti-P.
This is the same as in the case of d-Ni alloy.

Finally, Muk 5 to M 28 show the corrosion results of quaternary or higher alloys. Corrosion resistance is clearly improved compared to ternary alloys. This shows that a new alloy with excellent corrosion resistance has been obtained even in quaternary or higher alloys.

Table 2 shows the corrosion test results at 5 HC'l.

When compared with 1% H, So, the overall corrosion rate increases due to the harsher corrosive environment, but the alloy of the present invention is still superior to conventional corrosion-resistant titanium alloys.

Margin below Table 1 Overall corrosion test results 1'LH, So4. ss Table 2 Overall corrosion test results 5chi MCI, boil Next, the crevice corrosion test results are shown in Table 3.

Pure titanium and Ti-α15Pd alloys undergo crevice corrosion in less than a day. Ti-Q, 8Ni-OJM
o is.

After 2 days, crevice corrosion occurred. In comparison, it can be seen that the two alloys of the present invention all have higher crevice corrosion resistance.

Table 3 Crevice Corrosion Test Results 10 *NaCl, boiling, pH=&1 or 9 In addition to the above corrosion resistance, the alloy of the present invention is also excellent in hydrogen absorption resistance. Table 4 shows the test results.

This theta uses platinum as the counter electrode, and the voltage between electrodes is 6, OV.
As a result, hydrogen bubbles were emitted from the surface of the sample material to absorb hydrogen.

It can be seen that the amount of hydrogen absorbed by the alloy of the present invention is clearly lower than that of pure titanium.

Table 4 Hydrogen absorption test results Average level 2 The alloy of the present invention has strong corrosion resistance against extremely corrosive acids such as hydrochloric acid and sulfuric acid, but also strong non-oxidized formic acid, and also has excellent resistance to crevice corrosion. It also has excellent hydrogen absorption resistance.

From this, it can be seen that the alloy of the present invention is a completely new titanium alloy that overcomes the drawbacks of existing corrosion-resistant titanium alloys and has superior corrosion resistance.

Claims (1)

[Claims] Palladium 0.005 wt% or more and 2.0 wt% or less, nickel 0.01 wt% or more and 2.0 wt% or less, tungsten 0.005 wt% or more and 0.5 wt% or less, molybdenum 0.01 wt% or more A titanium-based alloy with excellent corrosion resistance, containing 1.0% by weight or less of one or more alloying elements selected from the group, with the remainder being titanium and unavoidable impurities.