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TECHNICAL INFORMATION
MODERN M A T E R I A L S FOR GAS T U R B I N E BLADES AND D I S C S
(UDC 669.14.018.45 : 682.135)
E. E. L e v i n
Polzunov TsKTI Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 1,
pp. 67-70, January, 1966
In recent years the number of pumping stations has increased greatly along with the development of gas pipe-
lines and the installation of powerful gas turbines for peak production at electric power stations. The main parts in these pumps require heat resistant materials which can be operated for 50,000-100,000 h. In some cases the work-
ing life of turbine blades is as low as 10,000 to 20,000 h under the highest permissible working temperatures. The
turbine blades and discs must be made of particularly strong materials since they are operated under severe conditions.
To withstand the influence of prolonged exposure to high temperatures the metal must have a stable structure,
high deformability, and (particularly important) low sensitivity to stress concentrators.
The increase in the temperature of the gas to 800-850~ and, correspondingly, of the temperature of the turbine
blades to 750-800~ increases the danger of breakage as the result of general and pitting corrosion and thermal fatigue.
There are many alloys manufactured at home and abroad which have high heat resistance at room temperature and
at workitlg temperatures and which are scale resistant [1-3J, but the selection of materials for turbine blades is
rather difficult.
1Kh12VNMF steel and the austenitic steels 3Khl9NgMVI3T and KhN35VT (EI612 and EI612K) are usually used
for blades and discs which are operated at 580-650~ An increase of the working temperature to 700-750~ leads
to the necessity of using nickel alloys - KhNSOTBYu (Et607, EI607A), KhNTOVMYuT, and Kh15N65V10M5TYu. The
EIg07A (KhNSOTBYu) alloy is used for blades in mass produced turbines operated at temperatures up to 200-720~
The addition of niobium to these alioys ensures uniform grain size and renders the mechanical properties
highly isotropic, which makes the ~I607A alloy a promising material for the manufacture of highly stressed discs.
The stronger KhTOVMYuT and Kh15N65V10M5TYu al!oys are used for blades operated at 720-750~ The
large total amount of molybdenum and tungsten in these alloys makes it difficult to manufacture large ingots and
forgings with large cross sections. Zonal liquation develops and, as the result, the properties of the different parts
are different. The uniformity of the properties can be increased by multistage heat treatment. This t reatment is
the most effective in the case of the KhN65VMTYu alloy. This alloy has very stable properties during prolonged
use and possible short periods of over-heating.
Further increase in the working temperature of blades to 800~ with possible short periods of over-heating
to 850~ makes it necessary to use alloys of a similar type but containing a high concentration of aIuminum. Ex-
haustive studies showed that the most promising alloy for these conditions is the EI826 altoy [1]. This alloy has
TABLE 1. Concentration of Different Elements in Nickel Alloys [1, 4]
Alloy No.
KhN80TBYu * ,. KhN80TBYu (EI60JA) * KhNTOVMYuT KhN65VMTYu EI826
<0,08 <0.08
0.10--0.16 <0.08 40.12
Chemical com ~osition, %
Cr
15--18 15--17 14--15 15--17 13--16
Ti
1.8--2,3 1,4--1.8 1.0--1,4 1".2--1,6 1,7--2.2
AI
0.5--1 0 0.5--1.0 1,7--2.2 1,2--1,6 2_4--2.9
No
ao--5.o 4.0--5.0 2.5--4.0
w
4.0--6 0 8.0--10 0 5.0--7.0
73
TABLE 2. Mechanical Properties of Nickel Alloys
Alloy No.
KhN80TBYu
KhN65VMTYu
J EI826
Aging conditions
TcmP., Time, ~ h
& 700 5000
Testing /-~0,~ I
temp. , C l kg /mm 2
20 650 700 650 700
60 105 55 75 50 68 60 90 38 63
26 lo
18 15
770 5000
20 700 750 750
67 55 52 42
105 80 78 75
30 20 20 29
750 800
5000 5000
20 700 800 750 800
62 52 50 60 45
107 95 80 95 65
17 23
12
32 12 7
18 18
35 30 23 35
16 27 25 16 20
a H , kgm/cm 2
10 10 12
10 12 12
3,5 6 7
7
TABLE 3. Resistance of Nickel Alloys to Prolonged Exposure to High Temperatures
A l l o y No.
KhN80TBYu KhN80TBYu (EI607A) KhN~0VMYuT ~hN65VMTYu EI826
O'prol, k g / m m 2 a t t he f o l l o w i n g t e m p e r a t u r e , OC
t 30/28 20/18 - - 25/23
25/24 50/47 38/37
800 j gSo
_ _ ) / _ _
lSTi~ t [ -- 18f20 --~13 - - 30/28 18/16/ 1U9
Note: The numerator refers to 5,000 h tests, the denominator to 10,000 h tests.
TABLE 4. Mechanical Properties of Alloys
t Aging conditions Heat t rea tment - -
Temp. , Time, conditions ~ h
Testing temp. , ~C
I ':0,2
k g / m m 2 a H , k g m / c m 2
1080 ~ C 6 hq-lO00 ~ C 2 h ~ - 7 5 0 ~ C
20 h
1120 ~ C 8 h+lO0O ~ c 4 hq-800 o C
16 h
& 650 700 700
& 650 700 700 750 750
KhNSOTBYu (EI607A)
100-00 10000 10000 10000
20 84 650 60 700 58
20 99 650 78
20 88 700 54
ksg8
- - 20 115 - - 650 96
700 90 10000 20 122 10000 650 108 10000 20 118 10000 700 91 10000 20 110 10000 750 75
47 47 32 38 35 25 54 26 44 22 40 3,0 33 40
70 31 57 27 59 20 80 14 67 19 69 20 57 27 58 25 45 30
47 44 37 30 28 30 45
31 30 23 15 24 19 35 25 40
16
6.0
7.2
9
3.3
3.4
6.5
74
TABLE 5.
Alloy No.
KhN80TBYu Y
(EI607A)
J EI698
KhN77TYuR
KhN70VMYuT
Resistance of Alloys to Prolonged Exposure to High Temperatures
~M
Testing
I temp. , ~
650 700
650 700 750
650 700 750
650 700 750
=prot, k g / m m 2 after the following testing t ime , h
300
54 32
64 52 36
54 40 27
R
500
56 30
61 47 33
50 38 25
m
I000
42 28
58 42 30
45 32 20
'314835 22--25
2000
38 26
56 37 27
42 28 17
274031 20--23
3000
37 25
54 35 25.5
40 27 16
5000 10000
35 33* 23 21"
52 33 21.5*
38* 25--22
15"
25~27 17--20
49* 29 19.0"
33* 20*
11--14"
37* 22--24 16--17
* Extrapolated data.
high plast ici ty at 650-850~ has a low sensit ivity to stress concentrators, and is highly scale resistant. The chemi- cal composit ion, the mechanica l properties, and the resistant of the nickel alloys to prolonged exposure to high temperatures are given in Tables 1-3.
The increase in the working temperature and stress and the need to decrease the britt leness lead to the ne- cessity of using nicket alloys for discs [2, 8],
Investigations of forgings of the KhN80TBYu (EI607A) alloy 450 and 6~0 mm in diameter and stampings of the EI698 alloy 480 and 850 mm in diameter showed that both alloys have good technological properties. The grain size of the forgings is uniform and there is no carbide l iquation or other macrodefects. The KhN80TBYu (EI607A) al loy was used for discs operated at 700-720~ The EI698 alloy, which has a higher aluminum, t i tanium, and niobium concentration and also contains molybdenum (_<0.08% C, 13.0-16.0% Cr, 2.0-2.6% Ti, 0.95-1.45% A1, 1.7-2.5% Mo, 1.6-2.1% Nb, the rest n ickel is recommended for discs operated at 750-760~
Tables4 arid 5 show the mechanica l properties of the alloys after heat t reatment determined on tangential samples. The properties of the metal in the tangential , axial , and radical directions are isotropic. Both alloys are character ized by low sensit ivity to stress concentrators.
Further increase in the temperature and stresses of the blades and discs of gas turbines leads to complex tech-
nological problems related to casting, forging, and stamping of large ingots and articles of highly al loyed alloys which are difficult to deform and problems rela ted to the creat ion of dependable coatings capable of protecting the surface of machine parts against the corrosive action of aggressive gaseous media.
L I T E R A T U R E C I T E D
1. F . F . Khimushin, Heat Resistant Steels and Alloys [in Russian], Moscow, Metal lurgiya (1964). 2. C. Howard, "Metal1 Progress" (1965), Vol. 3. 3. C. Howard, "Meta l l Progress" (1965), Vol. 4.
75
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