hastelloy B-4 is a new generation of Ni-Mo corrosion resistant alloy developed by KRUPP VDM of Germany, which is almost the same as B-3 alloy. The purpose of developing B-4 alloy is also to solve the mid-temperature hot brittleness and weld cracking of B-2 alloy due to the precipitation of p(Ni4Mo) phase. The method is also to adjust the Fe and Cr content in the alloy to suppress the precipitation of p phase. Or postponed, the difference between the two is that the B-4 alloy focuses on increasing the Fe content, while the B-3 alloy controls the Fe and Cr in the alloy simultaneously. Due to the high Fe content, the B-4 alloy has better control effect on the P phase than the B-3 alloy. The Mo content of the B* alloy is unchanged, and the alloy maintains the general corrosion resistance of the B-2 alloy. The thermal stability is significantly improved, the brittle crack tendency of the B-2 alloy during processing and manufacturing is overcome, and the intergranular corrosion resistance and stress corrosion resistance associated with thermal stability are also greatly improved.
7. 3. 4. 1 Chemical composition and structural characteristics
The chemical composition of 00Mo28Ni65Fe4Cr is shown in Table 7-6. This chemical composition has been adjusted from the earlier published ingredients, mainly because the upper and lower limits of the iron content in the alloy are relaxed by 1% (1% to 6%), and the data published in 1994 is 2% to 5%. The recommended Mo content is 28%, Fe is 3% and Cr is 1.3%. The thermal stability data shows that as long as w(Fe) is more than 3%, w(Cr) >0.5% can achieve the expected effect of the thermal stability of the alloy to meet the processing needs.
7.3.4.2 Mechanical properties at room temperature
The room temperature mechanical properties of 00Mo28Ni65Fe4Cr (B-4) alloy are basically the same as those of B-2 alloy and B-3 alloy. The room temperature mechanical properties of alloys with different Fe and Cr contents are shown in Table 7-48.
Table 7-48 Mechanical Properties of 00Mo28Ni65Fe4Cr(B-4) Alloy at Room Temperature
|
alloy |
w( Fe)/% |
tv(Cr)/% |
Rm/MPa |
Rp0.2/MPa |
A/% |
|
1 |
3. 17 |
1.42 |
857 |
375 |
71 |
|
2 |
3.23 |
0. 72 |
853 |
385 |
70 |
|
3 |
5.86 |
0.78 |
860 |
387 |
66 |
|
B-2 |
0. 11 |
0.02 |
914 |
424 |
62 |
|
B-3 |
1.75 |
0. 68 |
847 |
426 |
61 |
|
ASTM |
5=760 |
350 |
40 |
The high temperature instantaneous tensile properties can be referred to the data of B-3 and B-2 alloys.
7.3.4.3 Thermal stability of 00Mo28Ni65Fe4Cr (B-4) alloy The iron in Ni-28Mo alloy has a significant effect on the inhibition or retardation (3 phase (Ni4Mo) precipitation, as shown in Figure 7-14. The test indicates that it contains 5.86. The F-notch impact absorption of %Fe, 0.78%Cr, after aging at 650 °C, 700 °C, 750 °C and 800 °C for 1 h is greater than 140 J. This alloy has good moderate temperature aging thermal stability. The room temperature elongation after 700 ° C x 1 h aging also indicates that the B-4 alloy has good thermal stability (Table 7-49).
Table 7-49 Ageing Thermal Stability of B-2 Alloy and B-4 Alloy
|
alloy name |
Heat treatment state |
A(700°C)/% |
|
00Mo28Ni69Fe2(hastelloy B-2) |
700°C x 1 h |
5 |
|
control Fe、Cr (B-2) |
700°C x 1 h |
42 |
|
B-4(2% ~5%Fe, 0. 5% ~1.5%Cr) |
700°C x 1 h |
46 |
7. 3. 4. 4 Corrosion resistance
A general corrosion
Since the main corrosion-resistant alloying element Mo of 00Mo28Ni65Fe4Cr (B-4) alloy is the same as that of B-2 alloy, its general corrosion resistance is consistent with that of B-2 alloy. The corrosion test results in hydrochloric acid medium also show that the corrosion resistance of the two alloys is the same. Level.
B intergranular corrosion
00Mo28Ni65Fe4Cr (B-4) alloy, because its thermal stability is better than 00Mo28Ni65Fe2 (B-2) alloy, so under severe sensitization conditions, B-4 alloy has better intergranular corrosion resistance than B-2 alloy. See Table 7-50. These data indicate that the standard composition grade of Hastelloy B-2 alloy or the grade that controls the Fe and Cr contents within the specified standard composition. It can withstand sensitization at 600~900 °C for 1h, and its corrosion rate remains at the level of solid solution. When the sensitization time is increased to 8h, the sensitization temperature of 700 ft is 0.87mm/a. The solid solution state is twice as large, and the intergranular penetration depth is also more than 50 x 10 _6 m. The corrosion rate of the remaining sensitization temperature remains at the same level as the solid solution state. Under the same test conditions, sensitized at 600 ~ 900 °C for 8h, no intergranular corrosion was observed in B-4 alloy. 700 ° C is the most sensitive temperature for intergranular corrosion of B-2 alloy. The sensitization behavior of B-4 alloy in boiling 10% HC1 is shown in Table 7-51.
Table 7-50 Corrosion resistance of 00Mo28Ni65Fe4Cr(B-4) alloy in HC1 acid
|
alloy name |
corrosion rate/ |
mm • a_i① |
Intergranular penetration depth in heat affected zone of weldment |
|
boiling 10%HCl 24h |
boiling 20% HCl 24h |
/pm②（20% HCl，149°C，100h) |
|
|
B-2 alloy (0. 08% ~ 1. 75% Fe, 0.01% ~0. 68% Cr) |
0.29 -0.31 |
0:58-0.60 |
10 – 100 |
|
B-4 alloy（3.17% ~5. 68% Fe, 0. 72% ~1.42%Cr) |
0.24-0.38 |
0.46-0.58 |
0-170 |
Xl0-6m.
|
Sensitized (aging) temperature/°C |
corrosion rate/mm – a-1 |
|||||
|
B-2 alloy |
B-4 alloy |
|||||
|
0.5h |
lh |
8h |
0.5h |
lh |
8h |
|
|
600 |
0. 32 |
0. 29 |
0.39 |
0. 18 |
0.33 |
0.31 |
|
650 |
0.33 |
0. 38 |
0. 39 |
0. 27 |
0. 37 |
0.31 |
|
700 |
0. 35 |
0.36 |
0. 87° |
0.27 |
0. 32 |
0. 26 |
|
750 |
0.35 |
0.35 |
0.39 |
0.24 |
0. 35 |
0.29 |
|
800 |
0. 33 |
0.31 |
0. 33 |
0.25 |
0.23 |
0.25 |
|
850 |
0. 32 |
0. 32 |
0.31 |
0. 34 |
0.20 |
0.25 |
|
900 |
0. 30 |
0. 27 |
0. 34 |
0.21 |
0.24 |
0. 18 |
|
Solution annealed state |
0. 37 |
0.21 |
||||
The stress corrosion test of 00Mo28Ni65Fe4Cr (B-4) alloy U-shaped specimens in boiling 10% H2S04* according to ASTM G-30 procedure shows that the stress corrosion resistance of B-4 alloy is much better than that of standard B-2 alloy. It is also superior to B-2 alloy which controls the Fe and Cr contents (Table 7-52). The data in the table indicates that there is no difference in the stress corrosion resistance of the tested alloys in the solid solution state, and the difference at 700T is quite different. After 700T sensitization for 1h, the standard B-2 alloy showed stress corrosion for 3h, that is, B-2 alloy with Fe content at the upper limit of the standard, stress corrosion occurred at 45h, and no stress corrosion occurred after Bh alloy test for 100h. The sample is intact. The analysis of the 7001 sensitized sample after fracture shows that there are M6C and M2C type carbides in the grain boundary, and there are fine diffused Ni4Mo intermetallic compounds in the crystal. These aging precipitation phases cause the aged B-2 alloy to be sensitive to stress corrosion. The leading cause. The thermal stability of the B-4 alloy determines the excellent stress corrosion resistance of this alloy.
|
SCC time/h |
|||||
|
alloy name |
w(Fe)/% |
w( Ct)/% |
Solid solution state |
700^ x 1h aging |
700°C x5h aging |
|
B-2 alloy |
0.08 |
0.01 |
>100 |
3 |
2 |
|
B-2 alloy |
1. 13 |
0.47 |
>100 |
3 |
3 |
|
B-2 alloy |
1.75 |
0. 68 |
>100 |
45 |
3 |
|
B-4 alloy |
3. 17 |
1.42 |
>100 |
>100 |
>100 |
|
B-4 alloy |
3.23 |
0.72 |
>100 |
>100 |
>100 |
|
B-4 alloy |
5.86 |
0.78 |
>100 |
>100 |
>100 |
7.3.4.5 Hot cold processing, heat treatment, welding and physical properties
The hot and cold processing properties, heat treatment, welding and physical properties of 00Mo28Ni65Fe4Cr (B-4 alloy) are basically the same as those of B-3 alloy. The relevant data of B-3 alloy can be used.
7.3.4.6 Application
The application field of 00Mo28Ni65Fe4Cr (B-4) is the same as that of B-3 alloy.
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Post time: May-25-2019